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PLATE 27. V. I. p. 212.

Fig. 1. Lepidosteus osseus, or bony Pike of North America. (Agassiz. Vol 2. Tab. A.)

Fig. 2. Portion of the lower Jaw of Lipidosteus osseus, showing the occurrence of a row of larger conical hollow teeth, fluted externally, between two rows of smaller Teeth. (Original.)

2. a. Longitudinal section of a large Tooth, showing the internal hollow cone. (Original.)

2. b. Transverse section of a large Tooth. (Original.) Fig. 3. Transverse section of the Jaw. fig. 2. (Original.) Fig. 4. Fragment of a small upper Jaw of Megalichthys Hibberti, from Burdie house, showing a disposition of large and small teeth, similar to that in fig. 2. (Hibbert.)

4. a. b. Transverse section of the larger teeth. 4. c. Longitudinal section of a large Tooth.*

4. d. Punctate scale of Megalichthys.

Fig. 5. Aspidohrynchus: a fossil Sauroid fish from the Limestone of Solenhofen. (Agassiz, Vol I. Tab. F.)

PLATE 27. V. I. p. 212.

Amblypterus: one of the fossil fishes peculiar to the Carboniferous strata. Agassiz, Vol. I. Tab. A. fig. 3.)

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* It appears that in the Megalichthys and Holoptychus the structure of the teeth, both large and small, was precisely the same as in the large and small teeth of Lepidosteus osseus, both as to the hollow internal conical cavity, and the external flutings towards the base, and also as to their mode of growth by ascent of fibrous matter from the bony substance of the jaw, and not from roots placed in deep alveoli, as in many of the Saurians.

PLATE 27. Vol I. p. 214.

Fig. 1. Fossil fish of the genus Microdon, in the family Pycnodonts. (Agassiz, Vol. I. Tab. G. fig. 3.)

Fig. 2. Os Vomer of Gyrodus umbilicatus, from the Great Oolite of Durrheim, in Baden. (Agassiz.)

Fig. 3. Os Vomer of Pycnodus trigonus, from Stonesfield, Oxon. (Original.)

PLATE 27. V. I. p. 218, Note.

A. Teeth of a recent Shark, allied to fossil species.
Fig. 1. Anterior and Palatal Teeth of the Port Jackson
Shark, (Cestracion Phillippi.) (Phillip.)

Fig. 2. Anterior cutting teeth of Port Jackson Shark, in
the College of Surgeons, London. (Owen.)
Fig. 3. Flat tessellated tooth of the same. Nat. size. a.
Outer articular facet, showing the tubular structure
of the bony base. b. Punctate surface of the super-
ficial enamel. (Owen.)

Fig. 4. Mesial, and inner articular facet of another large tooth of the same. a. Upper concave margin thinly covered with enamel. b. Lower bony margin without enamel. a'. b'. Bony base of the tooth exposed by removal of the Enamel. The surface is areolar, from the bending and blending together of the bony tubes. c. c'. Fractured edge of the marginal and superficial enamel. (Owen.)

Fig. 5. Another anterior cutting tooth. a. Smooth enamelled point. b. Minutely rugous and tuberculated base. In some of the cutting teeth both sides of the base are rugous. (Owen.)

B. Various forms of fossil Teeth, in the three sub-families of Sharks. (B. 1. to B. 13. Agassiz.)

Figs. 1-5. Teeth of fossil Sharks in the sub-family of Cestracionts. See V. I. p. 218.

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 V. 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 V. 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.)

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 Chimæra, 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 Chimera 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 Chimera 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.

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.)

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