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Fig. 1. Psammodus, from Mountain limestone, Bristol. Fig. 2. Orodus, from the same. Fig. 3. Acrodus, from the Lias, Lyme Regis. Fig. 4. Ptychodus, (upper surface) from the Chalk. Fig. 5. Side View of fig. 4. Figs, 6–10. Teeth of extinct fossil Sharks in the subfamily of Hybodonts; in this family the enamel is plicated on both sides of the teeth. See W. I. p. 219, Note. Fig. 6. Side view of tooth of Onchus, from the Lias at Lyme Regis. Fig. 7. Front view of the same. Figs. 8. 9. 10. Teeth of Hybodonts, from the Oolitic slate of Stonesfield, Oxon. Figs. 11. 12. 13. Fossil Teeth of true Sharks in the Squaloid division of that family, having the Enamel smooth on the outer side. From the Chalk and London clay. See V. I. p. 220, Note. Fig. 14. Palatal teeth of Myliobates striatus, from the London clay of Barton cliff, Hants. See W. I. p. 221. Much of the enamel is worn away by use, as frequently happens in the tongue and palatal bones of living Rays. (Original.) C. Petrified remains of an extinct Genus of Shark. Fig. 1. Jaw of Hybodus reticulatus, from the Lias at Lyme Regis. (scale one half.) Many of the Teeth retain their place on the margin of the bone. The granulated structure of bone is distinctly preserved. (De la Beche.) Fig. 2. Teeth selected from the Jaw last figured. Nat. size. Fig. 3. Ichthyodorulite, from the Lias at Lyme Regis, being the Dorsal spine of Hybodus incurvus, set with teeth-like hooks, to suspend the membrane of the dorsal fin. (De la Beche.)
ExPLANATION OF PLATE 27°. 47
A double row of similar hooks occurs on the first dorsal ray of the Barbel, (Barbus Vulgaris.) And on the anterior ray both of the dorsal and anal fins of the Carp, (Cyprinus Carpio.) Fig. 4. Transverse Section of fig. 3, at a.” (De la Beche.)
PLATE 27°. V. I. p. 220.
Fig 1. Portion of the palatal teeth of Acrodus nobilis, resembling a cluster of contracted Leeches. These teeth are in their natural place, adhering to the curved granular bone of the palate, which is well preserved, and impregnated with Carbonate of lime. (Miss S. C. Burgon. Original.) Fig. 2. Continuation of the three rows of teeth on the reverse of fig. 1. Scale one half. (Original.) Fig. 3. One of the largest teeth on the centre row, having the upper part of the Enamel worn away by friction. Nat. size. (Original.) Fig. 4. Magnified view of the minute tubercles of Enamel which grew upon the skin; the decay of the skin
*In the Lond. and Edin. Phil. Mag. Jan. 1836, the author has published a notice of his recent discovery of the jaws of four extinct species of fossil fishes of the genus Chimaera, a genus hitherto unknown in a fossil state. The only known species (C. monstrosa) approximates most nearly to the family of Sharks; and is found pursuing Herrings and other migratory fishes. The Chimaera is one of the most remarkable among living fishes, as a link in the family of Chondropterygians; and the discovery of a similar link, in the geological epochs of the Oolitic and Cretaceous formations, shows that the duration of this curious genus has extended through a greater range of geological epochs, than that of any other genus of fishes yet ascertained by Professor Agassiz, and leads to important considerations in Physiology.
The Chimaera partakes of one remarkable character with the Cestracion Phillippi, whereby this species alone, among living Sharks, is connected with the extinct forms of that family, in having the first ray of the dorsal fin enlarged into a strong bony spine armed with sharp hooks, like the Ichthyodorulite of the earliest fossil Sharks.
48 ExPLANATION of PLATEs 27s. 28.
has brought clusters of these tubercles into contact with the bone in several parts of fig. 1. (Original.) Fig. 5. Magnified view of similar minute tooth-like tubercles of Enamel, forming the Shagreen on the skin of the head of the recent Squatina angelus. See V. I. p. 205, Note. (Original.)
PLATE 27. V. I. pp. 217 & 220.
Beautiful cluster of palatal teeth of Ptychodus polygyrus, from the Chalk. Insulated teeth of many species of this Genus abound throughout the Chalk formation. The mouth of these and all the other numerous extinct species of Sharks in the family of Cestracionts, was lined with a pavement of similar powerful teeth, forming a most efficient apparatus, for crushing the shells of Crustacea and Conchifera, which probably formed their principal food. The surfaces of the Enamel are often worn away, like that at Pl. 27°. fig. 3. The strength and efficacy of these teeth, viewed as Instruments for crushing shells, is very remarkable. Beneath the Enamel, the body of each tooth is composed of a strong mass of bone. (Miss F. C. Burgon. Original.)
PLATE 28. V. I. p. 230.
Fig. 1. represents the common calmar or squid (Loligo vulgaris, Lam. Sepia loligo, Linn.) showing the place and excretory duct of its Ink bag, and the position of the feet on the anterior margin of the head. (Blainville.)
Fig. 2. Side view of the Pen of the Loligo vulgaris, showing its position in the back of the animal, fig. 1. (Original.)
Fig. 3. Concave under surface of the same pen. (Original.)
-> ExPLANATION OF PLATE 28. 49
Fig. 4. Convex upper surface of portion of another recent pen, of the same kind. The structure of figs. 3 and 4 closely resembles that of the fossil species represented at fig. 6, of this same Plate, and also at Pl. 29. fig. 1. and Pl. 30. In all of them, the horny plates are composed of a series of longitudinal fibres, intersected by another series of transverse fibres. The disposition of the transverse fibres is most simple in the recent species; passing obliquely outwards from each side of the central shaft, like the barbs or fibrils in the vane of a feather, and being the most distinct towards the outer margin. The longitudinal fibres are scarcely visible in the recent species, except where they are collected into fluted fasciculi, Pl. 28. fig. 4. BB.) in those parts which correspond with the marginal bands of the fossil species. (Original.) C. Central part of the Pen, raised like the shaft of a quill between its fibrils. Fig. 5. Ink bag of a recent Cuttle fish, dissected by the author at Lyme Regis, 1829, containing its natural Ink in a desiccated state; it is a black shining Jet-like substance, having a splintery fracture, and resembling the substance and fracture of the fossil Ink. Its bulk is not much reduced by desiccation. (Original.) Fig. 6. Upper convex surface of a fossil pen of Loligo Aalensis from the Lias of Lyme Regis. A.A. the barbs; B.B. the marginal bands; C. axis of the shaft; D. excretory duct of the Ink bag, distended with petrified Ink." (Original.)
* In this specimen we see distinctly the disposition of the marginal bands.
ExPLANATION OF PLATE 29.
7. Upper surface of Fossil Loligo from the Lias of Lyme Regis. A, A, Barbs of the Pen. B,B, Marginal bands. C, Axis of the Pen. d, upper plate of marginal band, having an unusually corrugated surface, which may be the result of imperfect growth of the transverse fibres; if fully expanded they would probably have resembled those of the subjacent Plate at d". (Original.)
d'. Magnified representation of the rugous surface of d. d". Magnified representation of the second plate of the
marginal band, Fig. 7. d".
e. Upper surface of second Plate of the shaft of the pen;
here the transverse wavy lines predominate over the vertical straight lines; but both are visible.
f. Upper surface of third plate; here the vertical straight
fibres prevail ove: the transverse wavy fibres.
PLATE 29. V. I. pp. 232 and 234.
Fig, 1. Fossil Loligo from Lias at Lyme, in the col
lection of Miss Philpot, exhibiting nearly the same