382 [April 17, 



Jialocyon, a species common to the chalk of England, continental 

 Europe, and North America. Of the Placoid remains, two species 

 only belong to the section of the Squaloid family with serrated 

 teeth, and both of them are referable to the genus Corax, which 

 Agassiz informs us is restricted to the chalk. One species is not 

 distinguishable from Corax pristodontus of the Maestricht beds. 

 The other is undescribed. The Squaloid teeth with cutting edges 

 compose the bulk of the collection. They are referable to at least 

 a dozen species, all corresponding in the absence of plaits or strise 

 on the surfaces of the enamel. Although there are close approxi- 

 mations amongst them to the species both of the Cretaceous and 

 Miocene period, yet it is somewhat remarkable that I have not 

 seen a feature nor a character which recalls in the remotest degree 

 the forms of the Eocene period. They belong principally to the 

 Odontaspid type ; one species being closely allied to, if not identi- 

 cal with, the Odontaspis rhaphiodon of the chalk of Europe. Two 

 or three species are referable to the genus Otodus, one approach- 

 ing Otodus appendiculatus ; also from the chalk. Of the genera 

 found in the Pondicherry beds, the following is the stratigraphical 

 distribution assigned by Agassiz. The genera Lamna, Odontaspis, 

 and Oxyrhina extend from the recent period to the Green-sand 

 inclusive, the Jurassic species being now separated from Lamna 

 under the generic title of Sphenodus, and from Oxyrhina under that 

 of Meristodon. Otodus extends from the Crag to the Green-sand, and 

 Corax is restricted to the true chalk. The Ganoid genus Sphce- 

 rodus ranges from the Tertiary beds to the Oolite, and the Cycloid 

 Enchodus is restricted to the chalk. The distribution of species is as 

 follows : — Lamna, 5 tertiary and 1 cretaceous ; Odontaspis, 5 

 tertiary, 4 cretaceous ; Oxyrhina, 1 1 tertiary, 2 cretaceous ; Otodus, 

 8 tertiary, and 5 cretaceous ; and Corax, 5 cretaceous. Of the 

 five Placoid genera we have twenty-nine species occurring in the 

 Supercretaceous, and seventeen in the cretaceous deposits ; but 

 not a single species has yet been found anterior to the latter period. 

 The evidence, then, affoi'ded by the Pondicherry fishes appears to 

 yield strong corroborative testimony to the accuracy of Mr. Forbes's 

 views, derived from the study of the invertebrate remains of the 

 same locality ; and I fully coincide with him in assigning these 

 strata to the ci'etaceous period. I am, however, inclined, consider- 

 ing the number of species collected which must be referred to 

 genera which we know decrease in species as they descend in the 

 stratigraphical scale, from the occurrence also of Maestricht species, 

 and from the presence of the genera Corax and Enchodus not yet 

 found so low as the Neocomian, to place this deposit higher in the 

 system than Mr. Forbes is inclined to do from his investigations. 

 As I have above stated, the Placoid teeth are for the most part 

 mutilated, rendering the generic identification a matter of much 

 difficulty and uncertainty, although the specific characters are 

 good and distinct. Agassiz says *, " It frequently happens that 



* Poissons Fossiles, vol. ili. p. 266. 



