,^^. EVOLUTION OF SHARKS' TEETH. 675 



So far as the complication of teeth is concerned, the various 

 processes thus appear to be the same in the highest as in the lowest 

 vertebrates ; and these are evidently to be regarded as the outcome 

 of one fundamental law. It is singular, however, that there is as 

 yet little or no evidence of the operation of this law in the inter- 

 mediate groups of Amphibia and ReptiHa, in which the dentition 

 consists almost invariably of isolated, simple, or crenated cones. 



REFERENCES. 



1. Davis, James W. — On the Fossil Fishes of the Carboniferous Limestone 



Series of Great Britain. Tyans. Roy. Dublin Sue, ser. 2, vol. i., 1883, pp. 327-600, 

 pis. xlii.-lxv. 



2. ,— On the Dentition of Pleuroplax {Pleurodiis). Ann. Mag. Nat. Hist., ser. 6, 



vol. v., 1890, pp. 291-294, pi. xiii. 



3. Newberry, J. S., and "Worthen, A. H. — Geological Survey of Illinois, vol. ii., 



1866, vol. iv., 1870. 



4. Owen, R. — On the Mandible and Mandibular Teeth of Cochliodonts. Geol. Mag., 



vol. iv., 1867, pp. 59-63, pis. iii., iv. 



5. St. John, O., and Worthen, A. H.— Geological Survey of Illinois, vol. vii., 



1883 



6. Traquair, R. H. — On a specimen of Psephodus magnus, Agassiz, from the 



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 Glasgou',vo\. vii., 1883, pp. 392-402, pi. xvi. 



7. Woodward, A. S.— On the Palaeontology of the Selachian Genus Notidanus. 



Geol. Mag., dec. 3, vol. iii., 1886, pp. 205-217, 253-259, pi. vi. 



. . — Catalogue of Fossil Fishes in the British Museum, part i., 1889. 



A. Smith Woodward. 



