FOSSIL FAUNA. 157 



PLATE LXIX. 



Fossil Fishes and Reptiles. 



Fig. 1. " A fossil body resembling part of a Tortoise, from Gloucestershire." — Mr. Parkimon. 

 This specimen is probably one of the mandibles of a remarkable extinct genus 

 [Ceratodus) of fishes, whose dental organs, like those of the recent Chimcera, consisted 

 of consolidated plates instead of separate teeth ; each side of the jaw was formed by 

 one of these mandibular processes; the upper margin is deeply undulated. The bone- 

 bed of the Lias at Aust CliiF near Westbury, Somersetshire, is rich in these remains. 



Fig. 2. The plastron, or inferior aspect of the carapace of a fossil Turtle {Chelonia breviceps), 

 from the London Clay of the Isle of Sheppey. a, fragment of the entosternal plate ; 

 b, b, hyosternal plates; c, c, hyposternals ; d, xipkisternals.^ 



Fig. 3. The cranium of the same species of Turtle, from the Isle of Sheppey. 



Equally rich in the remains of Chelonian reptiles, as in those of Fishes, Crustaceans, Serpents, 



and Mollusks, the little Island at the mouth of the Medway has yielded to the indefatigable 



researches of Mr. Bowerbank the most extensive series of fossil Turtles hitherto discovered in 



England. The various genera and species will be figured and described in a work now in 



progress by Professors Bell and Owen, under the auspices of the Palseontographical Society, 



Fig. 4. A Serpula {S. antiqiiata ?), from the chalk, Sussex. 



Fig. 5. A dorsal vertebra of a fossil crocodilian reptile {Steneosaurus), from the Oxford Clay of 

 Honfleur. a, b, costal depressions. 



Fig. 6. A dorsal convexo-concave vertebra of a crocodilian or ga vial-like reptile {Streptospondi/his) , 

 from the same locality. This figure shows the remarkable character whence the 

 name of this genus : the convexity of the body of the vertebra (a) being situated 

 anteriorly as in mammalia, the reverse of the position of the bones forming the 

 vertebral column in the existing Crocodilian s and Lacertians. b, the posterior 

 concavity ; c, a deep depression beneath the neural arch. 



Fig. 7. Sketch of the lower jaw of an extinct gavial-like reptile {Steneosaurus) : the vertebra, 

 fig. 5, probably belongs to the same species. From Honfleur. This figure, and 

 figs, o, 6, and 8, are copied from Cuvier, " Annales du Museam" 



Fig. 8. A caudal vertebra of the Fossil Animal of Maestricht [Mosasaurus] ; a, the chevron bone 

 or inferior spinous process {kwmapophysis) , anchylosed to the middle of the body of 

 the vertebra. 



Fig. 9. Fossil scale of a ganoid fish (probably Lepidotus), from Kent. 



Fig. 10. Fossil tooth of a fish of the Shark family [Notidanus microdon, of Agassiz,) from the 

 chalk of Kent. 



Fig. 11. Recent "tooth of one of the Dog-fish," (Mr. Parkinson,) for comparison with fig. 10. 



Fig. 12. Tooth of an extinct group of squaloid fishes {Ptychodus decurrens, of Agassiz,) from the 

 chalk of Kent.' 



Fig. 13. a ctenoid (or comb-like) scale of a fish, (probably of a species of Beryx^) from the 

 chalk of Kent. 



' See Parkinson, p. 269. " See Medals of Creation, vol. ii. p. 617. 



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