Charles Doolittle Walcott

“ The function of the proboscis and its terminal spines is unknown; it appears to be adapted to the gathering of food and conveying it to a mouth beneath the head, but it was probably used by the male to seize the female.
If we consider the appendage-bearing somites as the thorax, the abdomen is confined to the one elongated expanded somite I have referred to as the telson. This does not show evidence of segmentation unless there is a post-anal plate, which is very doubtful. None of the specimens of the male show any traces of caudal appendages. ”

“ A. G. Mayer, [7] but I found that the body of Pelagothuria was cylindrical; the disk an enlargement of the body at the base of the tentacles; and that the mouth opened at the dorsal surface, and the anus at the end of the proboscis-like lower portion of the body. In contrast the Middle Cambrian type had a true medusa-like umbrella; concentric subumbrella muscle band; spiral subhorizontal alimentary canal, with mouth and anus off to one side of the center; and, judging from what is known of the umbrella-like body, opening at the ventral surface. ”

“ WIWAXIA, new genus
The generic and specific descriptions are united under the description of the species.
Genotype.—Wiwaxia corrugata (Matthew) .
Stratigraphic range.—The stratigraphic range is limited to a band of dark siliceous shale about 4 feet in thickness forming a part of the Burgess shale member of the Stephen formation at locality (35k) near Burgess Pass, and on the slope of Mount Stephen it was found in the trilobite beds of locality (14s) . ”

“ Body elongate, slender. Head short and without a carapace. Thorax with eight segments. Abdomen with four segments, the posterior bearing a pair of expanded caudal rami.
Head sub-quadrangular in outline, composed of five coalesced segments, the posterior four of nearly equal width and the anterior narrow. The segmentation of the head is very plainly shown on some specimens (fig. 12) and not on others (fig. 10) . I have inclined at times to consider that there was a cephalic carapace, but finally decided that if present it was very small and thin and not to be recognized as a true carapace. ”

“ Subsequent formations of Cambrian age came in a great group of alternating shale and sandstone followed by an immense thickness of limestone and shale. Fossils of Cambrian age, mainly Olenellus, are found as far down as the middle of the sandstone group. The strata lying beneath the fossiliferous beds differ in no material respect from those overlying. All are plainly due to the same causes and form part of one and the same group, and all are closely associated in area and structure. ”

“ The oldest known representative of the Ostracoda is Indiana dermatoidea from the Lower Cambrian. [14] Several genera of ostracods range up through the Middle and Upper Cambrian. A fine, small species occurs in the Burgess shale. The Trilobita begins with Nevadia deep down in the Lower Cambrian [15] and predominates in all later Cambrian faunas.
I do not know of any genera of the Branchiopoda in the Cambrian other than those described in this paper from the Burgess shale and the single specimen of Protocaris from the upper part of the Lower Cambrian. ”

“ The cranidium is not unlike that of Coosia limbatum (Angelin) ; it differs in having a slightly convex or rounded frontal limb and proportionately narrower glabella. The pygidium is quite different in outline; the rounded indented posterior margin of A. limbatum is represented by a deep notch that gives a bilobed appearance to the very broad margin; the axial lobe is also longer and broader than that of A. limbatum. The doublure of the pygidium extends close up to the termination of the furrows of the pleural lobe. ”

“ The sediments of the two widely separated periods of Algonkian and Tertiary time were accumulated within the limits of the great Cordilleran geosyncline, and, with our present knowledge, I think, under essentially similar physical conditions. At the time of the Tertiary deposition there was abundant life, both on the land and in the water, but in Algonkian time only a fragment of the pre-Cambrian life had had the opportunity of adapting itself to the conditions of the inland seas of late Algonkian time. ”

“ The facial sutures cut the posterior margin just within the genal angle and extend obliquely inward with a slightly sigmoid curvature to the base of the eye lobes; curving over and around the eye lobes, they pass forward and a little outward, cutting the frontal margin obliquely.
Thorax with nine segments; axial lobe moderately convex, slightly narrower than the pleural lobes in compressed specimens; on the outer side of each segment a low rounded node or ridge is separated from the main body of the segment by a slightly oblique furrow transverse to the segment ”

“ One has a length of 61 mm. and the other of 52 mm., exclusive of any frontal appendages. The female differs from the male in having two slender caudal appendages or rami; and in having a slender bifid frontal appendage instead of the strong appendage of the male. The character of the frontal appendage is more or less doubtful as it is turned under and back on the side of the body. I hope that we will find in the collections of the summer of 1912 specimens that will add much to our knowledge of all parts of both the male and female of this species. ”

“ Generic name derived from Amiskwi, name of a river west of Mount Burgess, British Columbia, Canada.
AMISKWIA SAGITTIFORMIS, new species
Plate 22, figs. 3 and 4
Body cylindrical and divided into a broadly elongate oval head, a cylindrical body, and an expanded tail. The head, expanding from the neck, contracts to a bluntly pointed anterior end, from the rounded angles of which project a pair of strong tentacles. The lateral fins of the body are a little more than one-third the length of the body and quite prominent. The tail is expanded and slightly transverse at the posterior margin. ”

“ The stalked eyes are distinctly shown for Opabinia (pl. 28, fig. 1) , Waptia (pl. 27, fig. 4) , and Yohoia (pl. 29, fig. 9) , and for Hymenocaris by specimens not illustrated. Burgessia (pl. 27) and Marrella (pl. 25, figs. 4 and 5) have sessile eyes and five pairs of cephalic appendages. The sessile eyes, as in the trilobite, probably represent a segment of the cephalic shield.
The character of the several thoracic appendages is described under each species. ”

“ Abdominal.—A number of specimens show more or less of traces of abdominal appendages on the first nine segments of the abdomen. None of these indicates the presence of a jointed appendage in any way comparable with the appendages of the cephalo-thorax, or the abdominal appendages of the trilobite. The appendages appear to be formed of clusters of branchial fringes attached to short lobes that are round or oval in outline and affixed to the ventral surface on each side of the abdomen at the outer edge of its inner third, or they may be of a lamellated structure as shown by fig. ”

“ Owing to the Burgess shale member of the Stephen formation being overlain and underlain by massive limestones it is very frequently metamorphosed and cleaved into schists or soft calcareous or siliceous slates.
MODE OF OCCURRENCE
With the exception of Marrella splendens and Hymenocaris perfecta, Agnostus, and Microdiscus, the fossils are irregularly distributed and of relatively rare occurrence. They are pressed flat even in layers where there are no visible traces of lamination of the rock. ”

“ The theory that life originated and developed in fresh-water ponds and lakes does not appeal to me. More uniform conditions of temperature and environment would be present in the ocean and the sediments of the fresh-water deposits of pre-Cambrian and Cambrian time, if such exist, do not show sufficient evidence of life having existed at the time of their deposition. ”

“ Frontal limb broad and strongly concave in large cephalons, becoming less so in smaller; in front of the glabella it slopes rather rapidly downward and then upward with a gentle curve to the thin, rounded edge. Free cheeks gently convex, but become slightly concave toward the outer margin in the larger specimens. The genal angles are extended into short spines.
Thorax with eleven nearly transverse segments; axial lobe convex and a little more than one-half the width of the pleural lobes. It is strongly defined by a sharp angle where the segments pass into the pleural lobes. ”

“ Genus SIDNEYIA, new genus
Body elongate, broadly oval in outline, attaining as now known a length of 17 cm., covered with a thin dorsal shield or crust, divided into a short cephalon, broad anterior abdomen, and narrow posterior abdominal portion. Cephalo-thorax transverse, short, depressed convex, as compressed in the shale, with broadly rounded frontal margin and antero-lateral angles; margins smooth. Eyes reniform and situated near the postero-lateral outer margin. Ventral side with five pairs of movable appendages. The anterior pair are large, long, simple, jointed antennae ”

“ The carapace of Marrella (pl. 25, fig. 1) is most interesting. The eyes on the anterior margin, the large antennules (?) , and the great posterior dorsal spines indicate a great modification of and advance over the simple primitive shield resulting from a fold of the cuticle of the fifth segment of the head. The shield of Burgessia (pl. 27, figs. 1-3) is simple, and that of Naraoia (pl. 28, fig. 4) simple over the head and more complex over the thorax.
In Waptia (pl. 27, figs. 4 and 5) the shield has passed nearly to the bivalve stage of the Hymenocarina. ”

“ Observations.—This subgenus is characterized by a nearly smooth surface on the glabella and fixed cheeks, rather large palpebral lobes, and narrow postero-lateral limbs. Unfortunately, no entire specimens of the cephalon and thorax are known, and the pygidia referred to it may or may not belong to the species to which they are tentatively assigned. Only when a thorough study is made of all the material within the Conocephalinæ will it be possible to make even a fairly adequate grouping of the species. ”

“ The associated pygidium is large, with a strong axis, broad pleural lobes, and few indications of segments.
The general form of the glabella is much like that of some species of Anomocare (pl. 17) but the frontal limb is quite different. The latter suggests Pagodia lotos Walcott but the frontal limb of the latter is absorbed by the rounded frontal rim. In Chuangia the frontal limb and rim meet to form an angle and the rim does not rise above the upward sloping surface of the frontal limb. ”

“ The test is very thin and it has often been wrinkled and distorted in the shale. Ten specimens show it pressed down sideways so as to give the outline of a bivalve carapace (figs. 3 and 4, pl. 30) .
The thorax is slender and composed of 8 rather short segments that bear appendages.
The abdomen is composed of one segment that is about the size of the last thoracic segment; it is followed by a long, slender, many-jointed telson-like extension that tapers gradually to a very fine, thread-like extremity. An abdomen of one segment has a telson 21 mm. in length attached to a body 12 mm. ”

“ The annelids of the Burgess shale, like the holothurians and Medusæ, are pressed flat so that the animal is represented by only a thin film. Fortunately this is darker than the shale and usually shiny, and the contents of the animal are often preserved as a glistening silvery surface, even to the fine details of structure. How clearly the specimens exhibit both external and internal characters is shown by the plate figures which are reproduced from photographs made by reflected light. ”

“ Formation and locality.—Middle Cambrian: Stephen formation, Ogygopsis shale, west slope of ridge between Mount Field and Mount Wapta, about 3800 feet above Field on the line of the Canadian Pacific Railway, British Columbia, Canada.
A second species of this genus or a closely allied form occurs in the Redlichia chinensis zone of Indo-China. (See p. 19.) It is the oldest Merostome now known as it comes from the horizon of the Man-t'o shale formation of the upper Lower Cambrian terrane. [13] ”

“ The discovery of caudal rami on Neolenus (pl. 24, figs. 1 and 1a) still further accentuates the conclusion of Bernard that the trilobites were derived from the same stock as Apus. This is further strengthened by the presence in the Middle Cambrian of a form like Nathorstia transitans (pl. 28, fig. 2) , which is essentially a trilobite, but its setiferous thoracic appendages relate it closely to Opabinia regalis (pl. 27, fig. 6) .
Neolenus serratus (Rominger) .— A number of specimens of this species show the antennæ, jointed thoracic legs, and caudal rami. ”

“ Coosia daunus (Walcott) , [17] although having a similar frontal limb and form of glabella, undoubtedly belongs to a different genus or subgenus; this is indicated by its very strongly pitted surface.
A second species from Alabama, C. robusta (pl. 16, figs 2, 2a) , is illustrated for comparison as it has a well preserved cranidium and the pygidium is proportionately more elongate than that of C. superba.
Another form that is very close to this species is Anomocare limbatum Angelin. ”

“ Exumbrella with about thirty clearly defined lobes that radiate from the center to the edge of the disk. Each lobe has a slight depression or line down the center that extends in from the outer margin from one-half to two-thirds the distance to the center (pl. 12, fig. 3) . This secondary lobation gives about sixty slightly projecting, rounded lappets about the margin of the disk. In small specimens flattened sideways in the shale (pl. 11, figs. 1 and 2) , the secondary lobation is emphasized so that the narrow lobes (of the 60 series) extend inward toward the center. ”

“ The merostomes Sidneyia, [18] Amiella, [19] Habelia (pl. 29) , Molaria (pl. 29) , and Emeraldella (pl. 30) , have a compact cephalic shield and well-defined thoracic and abdominal segments and telson that are similar in character to the dorsal shield of the trilobite.
Labrum.—The labrum or hypostoma of Sidneyia [18] Emeraldella (text fig. 8, p. 204) , and Marrella (pl, 26, fig. 2) is clearly shown in a number of specimens, also that of Burgessia (pl. 27, fig. 2) , but in the other species it has not been seen nor has the lower lip (labium or metastoma) been observed in any species. ”