Charles S. Boyer

“ The sporangial frustules vary in shape and size, some being long and slender, others clavate, but they are all more or less tumid in the middle, with costæ more indefinite than in perfect valves. All gradations occur, one end becoming shorter until the valve has the shape of the variety known as constrictum. It would seem, therefore, that the non-constricted form is a passage from the sporangial to the smaller or adult form, or is of no specific importance. All forms are found living together. The adult frustules are the smaller ones ”

“ Frustules adnate in small stipitate clusters or free. Valve elongate, linear or linear-lanceolate; pseudoraphe distinct; costæ absent.
The genus Synedra has few distinctive characters. As Brun remarks (Diat. des Alpes et du Jura, p. 122) , the dilatation of the extremities and the pseudo-nodule are of little value in classification, as the intermediate forms are so numerous. Fragilaria occurs in very long ribbons or fasciæ, Synedra in short fasciæ or radiating clusters. Fragilaria is seldom longer than three or four times the width, while Synedra is nearly always so. ”

“ Valve arcuate, without costæ, transversely striated; pseudoraphe absent; pseudo-nodules at each end.
Chromatophores laminate along the concave zone and the valves.
Very many species of Eunotia have been created to differentiate size and number of crenæ or undulations. An examination of certain fossil deposits of New England, as well as a gathering from the blue clay of Philadelphia, will show forms which vary infinitely. E. major and E. gracilis are scarcely distinguishable because of the intermediate variations. The striæ in all forms are punctate, but the puncta are frequently confluent. ”

“ Synedra.—Valve elongate.
Asterionella.—Frustules in star-shaped clusters.
Fragilaria (Lyng.) Rab.
(fragilis, because of the fasciæ easily breaking up)
Frustules rectangular, adnate in fasciæ, soon breaking up. Valve lanceolate, oblong or elliptical in general outline, with convex or sinuate margins; without costæ; pseudoraphe narrow or indistinct; striæ transverse. Chromatophores vary according to species. In some they consist of four bands on the valves; in others they are granular (Mereschkowsky) . ”

“ Brun divides the genus into two sections, Fragilaria proper and Staurosira. The former, with an indistinct pseudoraphe, includes the species virescens, arctica, undata and linearis, while the latter, with distinct pseudoraphe, includes capucina, harrisonii, construens and parasitica.
FRAGILARIA VIRESCENS RALFS
Frustules in long fasciæ. Valve elliptical-lanceolate, obtuse at the apices; pseudoraphe indistinct; striæ, 17 in 10 μ, punctate.
Very common in springs and pure streams. The fasciæ are often a foot or more in length. ”

“ Frustules quadrangular, concatenate, composed of numerous septate partitions with transverse costæ or rows of puncta. Valves elliptical, with a pseudoraphe and transverse apparent costæ and punctate lines; the partitions with one or several foramina.
Chromatophores in rosettes of various kinds (Karsten) ; usually parallel to the septa.
RHABDONEMA ARCUATUM (LYNG.) KUETZ.
Valve hyaline at the ends, with transverse rows of puncta producing the appearance of costæ between the rows; pseudoraphe distinct; foramen single. ”

“ Frustules oblong or quadrate, adnate in filaments, attached by alternate angles and finally separating. Valve linear or elliptical, with transverse costæ and rows of puncta and a pseudoraphe.
Chromatophores large granules without definite arrangement. (See Pl. 40, Fig. 11.)
DIATOMA VULGARE BORY.
Valve elliptical-lanceolate, with apices sometimes rostrate or capitate; pseudoraphe narrow; costæ, 5 in 10 μ.
Common everywhere in pure fresh water and extremely variable.
Pl. 10, Figs. 9 and 10.
Var. elongatum (Ag.) = var. ehrenbergii (Kuetz.) —elliptical-lanceolate, constricted near the apex. ”

“ Valve linear with rostrate apices; costæ robust; striæ delicate, 20 in 10 μ. Zone view quadrangular.
Common in fresh water.
Pl. 10, Figs. 5 and 6. Fig. 11, Pl. 40, shows frustules containing the nuclei and chromatophores.
DIATOMA HIEMALE (LYNG.) HEIB.
Valve ovate-lanceolate to lanceolate; apices obtuse, not produced. Costæ not numerous, robust; striæ moniliform. Zone view quadrate, the costæ as septa deeply dividing the valve into convex elevations. ”

“ F. harrisonii is probably in any case to be separated from the others. De Toni includes it under its original name of Odontidium, which genus he places near to Diatoma. The number of species in our locality is too limited to render further discussion of any value.
Rhaphoneis Ehr. (1844)
(rhaphis, a needle)
Frustule in zone view linear. Valve lanceolate or elliptical-lanceolate; pseudoraphe distinct; striæ radiating, moniliform.
RHAPHONEIS AMPHICEROS EHR.
Valve lanceolate, broad, with apices produced; striæ in curved lines, moniliform, the large granules in longitudinal lines. ”

“ Valve lanceolate, tapering to the sub-acute, rostrate or slightly capitate apices; dilated at the central hyaline space; pseudoraphe distinct. Very variable in size.
Crum Creek. Schuylkill River. Rather common.
Pl. 11, Figs. 14, 15, 16.
SYNEDRA PULCHELLA VAR. ABNORMIS MACCHIATI?
Valve as in type form, except that one end is curved like a beak, as in S. hamata Wm. Sm., which it resembles.
Not uncommon in the Schuylkill River.
Pl. 11, Fig. 17.
SYNEDRA OXYRHYNCHUS VAR. UNDULATA GRUN.
Valve linear-lanceolate with produced rostrate apices, asymmetrical, sigmoid; pseudoraphe narrow ”

“ Reported by Kuetzing in the Atlantic Ocean and by Kain at Belmar, N. J. I have not found it on our coast and I believe, in some cases, it has been confused with G. angulosa var. hamulifera. The figure is drawn from an Iceland form in H. L. Smith T. S., 186. ”

“ E. enneadon (9) ; E. decadon (10) ; E. hendecadon (11) ; E. duodecadon (12) ; E. serra (13) ; E. prioritis (14) ; all more than 20, E. polyodon. E. scalaris, with from 15 to 17 crenæ, and E. icosodon with 20, may be added.
It is probable that all of these forms occur at May's Landing, N. J. The forms with more than eight crenæ are comparatively rare. In the blue clay those with from four to six are most common.
Pl. 13, Figs. 13, 14, 15, 16, 17, 21, 24, 25.
EUNOTIA BACTRIANA EHR.
Valve linear, apices revolute, acute, dentate on the dorsal margin, with one acute crena near each end. ”