Ichthyolith

“ Lying detached in the stratified clay of the fish-beds, there occur in abundance single plates and scales of ichthyolites, which, as they can be removed entire, and viewed on both sides, illustrate points in the mechanism of the creatures to which they belonged that cannot be so clearly traced in the same remains when locked up in stone. There is a vast deal of skilful carpentry exhibited—if carpentry I may term it—in the coverings of these ancient ichthyolites. ”

“ The two former reached their maximum in the earlier geological ages, and have been gradually dwindling down ever since, till now they are represented by comparatively few genera; the two latter are emphatically modern orders; they have been constantly increasing in numbers since their creation, and swarm in every sea at the present day. The carboniferous ichthyolites belong, of course, only to the two first-mentioned orders the placoids and ganoids. ”

“ An entire specimen has never been obtained; nor, from the destructible nature of the animal framework, can we expect to meet with one. But the hard bony parts of the animals, those capable in short of preservation in mineral accumulations, are of common occurrence in the mountain limestone beds and even among the coal seams. The dorsal spines or ichthyodorulites, are especially conspicuous (Fig. 28) . They stood up along the creature's back like masts, the fin which was attached to the hinder margin of each, representing - 117 - the sail. ”

“ In tracing the evidences of creative power from the earlier to the later formations of the earth’s crust, remains of the Ichthyosaurus are first found in the lower lias, and occur, more or less abundantly, through all the superincumbent secondary strata up to, and inclusive of, the chalk formations. They are most numerous in the lias and oolite, and the largest and most characteristic species have been found in these formations. ”

“ In most cases the organic substances undergo great changes in the bowels of the earth. The animal matter of the Caithness ichthyolites exists, for instance, as a hard, black, insoluble bitumen, which I have used oftener than once as sealing-wax; the vegetable mould of the Coal Measures has been converted into a fire-clay, so altered in the organic pabulum, animal and vegetable, whence it derived its fertility, that, even when laid open for years to the meliorating effects of the weather and the visits of the winged seeds, it will not be found bearing a single spike or leaf of green. ”

“ The range of the genus Ichthyosaurus seems to have begun with the Muschelkalk, and to have extended through the whole of the oolitic period into the cretaceous formation. The most recent stratum in which any remains of this genus have yet been found is the chalk marl at Dover, where they have been discovered by Mr. Mantell: I have found them in the gault, near Benson, Oxon. ↑ Pl. 7, is a large and nearly perfect specimen of the Ichthyosaurus Platyodon, from the lias at Lyme Regis, being one of the splendid series of Saurians, Purchased in 1834 of Mr. Hawkins by the British Museum. ”

“ Some few are much larger, and bear a due proportion to the gigantic calibre of the largest Ichthyosauri; others are small, and bear a similar ratio to the more infantile individuals of the same species, and to small fishes: some are flat and amorphous, as if the substance had been voided in a semifluid state; others are Battened by pressure of the shale. Their usual colour is ash-gray, sometimes interspersed with black, and sometimes wholly black. Their substance is of a compact earthy texture, resembling indurated clay, and having a conchoidal and glossy fracture. ”

“ And in little more than a fortnight he had detected the ichthyolites in numerous localities all over an Old Red Sandstone tract, which extends from the primary districts of Banff to near the field of Culloden. The Old Red Sandstone of the north, hitherto deemed so poor in fossils, he found—with the Cromarty deposits as his key—teeming with organic remains. In the spring of 1838, Dr. Malcolmson visited England and the Continent, and introduced some of my Cephalaspean fossils to the notice of Agassiz, and some of the evidence which I had laid before him regarding their place in the scale, to Mr. ”

“ In fine, the Ichthyolites of the different formations constitute two grand groups, which have their boundary line at the base of the Cretaceous deposits. The first and most ancient comprises the Ganoids and Placoids; the second, more intimately related to existing types, comprehends forms more diversified; these are principally Ctenoid and Cycloid, with a small number of the two preceding orders, which insensibly disappear; and their few living analogues are very distinct from the ancient species. ”

“ Lign. 203. Smerdis minutus. Eocene. (nat. size.)
Aix in Provence.
Osmeroides. Plate II. and Wond. p. 344, 347.—Two species of this genus occur in the Chalk, near Lewes; and principally, if not exclusively, in the Lower Chalk, without flints. They are exceedingly beautiful Ichthyolites, and are almost invariably found with the body but little compressed; the fish, in many examples, is as round and perfect as when living. The entire cranium, the opercula and branchial rays, and all the fins are preserved in some « 627 » examples. ”

“ They form a great contrast to the fish of the secondary strata, as, with the exception of the Placoids, they are all Teleosteans, only one genus, Pycnodus, belonging to the order of Ganoids, which form, as before stated, the vast majority of the ichthyolites entombed in the secondary are Mesozoic rocks.
Cretaceous Period.—M. Virlet, in his account of the geology of the Morea, p. 205, has clearly shown that certain traps in Greece are of Cretaceous date; as those, for example, which alternate conformably with cretaceous limestone and greensand between Kastri and Damala, in the Morea. ”

“ Some of the readers of my little work on the Old Red Sandstone will perhaps remember that I described the organisms of that ancient system as occurring in the neighborhood of Cromarty mainly on one platform, raised rather more than a hundred feet over the great Conglomerate; and that on this platform, as if suddenly overtaken by some wide-spread catastrophe, the ichthyolites lie by [Pg 193] thousands and tens of thousands, in every attitude of distortion and terror. ”

“ Ichthyolites of recent species.—The distinguished naturalist to whose labours in fossil Ichthyology we have been so largely indebted, states, that of the many hundred species submitted to his notice, but one can be identified with any fish now living. This conclusion must, however, be received with some reservation; for, among the fossil genera, founded on the teeth, there are species which certainly cannot be distinguished from recent forms. ”

“ We find, however, in some of the genera, portions of the animal preserved that are rarely [Pg 478] seen in a state of keeping equally perfect in the ichthyolites of Cromarty, Moray, or Banff,—those terminal bones of the Coccosteos, for instance, that were prolonged beyond the plates by which the head and upper parts of the body were covered. Wherever the ichthyolites are inclosed in nodules, as in the more southerly counties over which the deposit extends, the nodule terminates, in almost every case, with the massier portions of the organism ”

“ Ichthyosis is a chronic, hypertrophic disease, characterized by dryness and scaliness of the skin, with a variable amount of papillary growth.
At what age is ichthyosis first observed?
It is first noticed in infancy or early childhood. In rare instances it is congenital (ichthyosis congenita) , and in such cases it is usually severe, and of a grave type; the children are, as a rule, prematurely born, and frequently do not survive many days or weeks. ”

“ And its ichthyolites, if not previously absorbed, were probably destroyed in the convulsion. Detached scales and spines, however, if carefully sought for in the various openings of the valley, might still be found in the original laminæ of the fragments. They must have been amazingly abundant in it once; for so largely saturated is the rock with the organic matter into which they have been resolved, that, when struck by the hammer, the impalpable dust set loose sensibly affects the organs of taste, and appeals very strongly to those of smell. ”

“ In the genus Dendrodus, for instance, it is the generic type, that from a central nave there should radiate, spoke-like, a number of leafy branches; but in the several species, the branches, if I may so express myself, belong to different shrubs, and present dissimilar outlines. There are no repetitions of earlier patterns to be found among the generically different ichthyolites of other formations. We see in the world of fashion old modes of ornament continually reviving: the range of invention seems limited ”

“ It will be observed from the figures that the arm and thigh bones of Ichthyosaurus are very much shortened—a striking adaptation to water life, so conspicuously seen in the modern whales and dolphins as well as in the mosasaurs, thalattosaurs, etc. So characteristic indeed is this shortening that, were every other bone of the skeleton of an ichthyosaur unknown save the humerus or femur, it would be quite certain from these alone that the animal was thoroughly aquatic in habit. ”

“ The distribution of Ichthyosaurs in time and space is wide. The earliest are found in the Middle Trias; in the Lias they are very common, fairly frequent in the Oolites, dying out with the Cretaceous epoch. They have left no descendants, being far too specialised, and their origin is quite unknown. Mixosaurus, the oldest genus, occurred in Europe, and has also been found in the Triassic strata of Spitsbergen. Ichthyosaurus, the chief genus, is known from the Liassic, Oolite, and Cretaceous strata of Europe, a famous place being Lyme Regis ”

“ Ichthyol Albuminate, Knoll.—Gray-brown, odorl., almost tastel. powd.; 4 parts equal 3 parts ichthyol.—Sol. in alkaline fluids (such as intestinal secretion) ; insol. in ordinary solvents and in diluted acids (as gastric juice) .—Succedaneum for Ichthyol internally as an Alterant, Antiphlogistic, and Assimilative.—Uses: Phthisis, scrofula, rheumatism, skin diseases, etc.—Dose: 15—30 grn., 2 or 3 t. daily, before meals.— [Further information in "Merck's Digest" on "Ichthalbin," containing clinical reports and detailed information.] ”

“ The private collections of the locality, by forestalling, greatly restrict the supply from the rich deposits in the neighborhood, and have an unquestioned right to do so. The Museum contains, however, several interesting organisms. I saw, among the others, a specimen of Diplopterus, that showed the form and position of the fins of this rather rare ichthyolite much better than any of the Morayshire specimens portrayed by Agassiz in his great work; and beside it, one of the two specimens of Pterichthys oblongus which he figures, and on which he establishes the species. ”

“ Continuing our investigation, we next find the fruitful coal era passing away; scarcely a trace of vegetation remains; a few species of zoophytes, shells, and fishes are to be found, and we observe the impression of footsteps, technically called ichnites, from the Greek ichnon, a footmark. These marks present a highly interesting memento of past ages. Persons living near the sea-shore must have frequently observed the distinctness with which the track of birds and other animals is imprinted in the sand. ”

“ Or what would be the proper inference, were I to find one of the many-thorned ichthyolites of the Lower Old Red Sandstone with the spines of its pectorals similarly fixed on cubes of lignite?—that there had existed in these [Pg 272] early ages not merely physical death, but also moral evil ”

“ It descends in the fishes, both recent and extinct, to even the microscopic structure of their teeth; and we find, in consequence, not less variety of figure in the sliced fragments of the teeth of the ichthyolites of a single formation, than in the carved blocks of an extensive calico print-yard. Each species has its own distinct pattern, as if, in all the individuals of which it consisted, the same block had been employed to stamp it; and each genus its own general type of pattern, as if the same radical idea, variously altered and modified, had been wrought upon in all. ”

“ We see the spiked wings of the Pterichthys elevated to the full, as they had been erected in the fatal moment of anger and alarm, and the bodies of the Cheirolepis and Cheiracanthus bent head to tail, in the stiff posture into which they had curled when the last pang was over. In various places in the neighborhood the ichthyolites are found in situ in their coffin-like nodules, where it is impossible to trace the relation of the beds in which they occur to the rocks above and below ”

“ The genus Ichthyonema is confined to fishes. The male is very minute and the female partly degenerate. It has no anus and no external opening to its generative organs. The uterus fills up almost the whole of the body-cavity. I. sanguineum Rud. is found encapsuled in the peritoneum of many fish.
Hystrichis and Dispharagus are confined to birds, where they occur in the oesophagus and stomach. Spiroptera reticulata {150}Crep. occurs in horses, twisted in a spiral round tendons and muscles, forming tumours which require to be opened. ”