BRITISH FOSSILS. 



3 



other species of which the trunk is preserved, with the exception of 

 the species of Pycnodus orbicularisy in the Paris Museum, is the 

 small Pycnodus rhombus, found in the Jura (?) beds of Ton-e 

 d'Orlando, near Castel-a-Mare ; and in this older form this peculiar 

 character is less prominent. The remaining thirty-two species 

 enumerated and partly described in the "Poissons Fossiles," rangiug 

 from the tertiary formation down to the Keuper, are only known 

 by their teeth. It is, therefore,""' quite possible that the Oolitic 

 species may have resembled the other Pycnodonti of that period, in 

 the more rounded outline of the body, and that this must therefore 

 be considered a specific rather than a generic condition. Be this as 

 it may, the characters derived from the dentition are of so much 

 greater moment than the mere outward form of the fish, and they 

 coincide so entirely with those of the well-known dental apparatus 

 of the genus Pycnodus, that no doubt remains upon my mind as to 

 the propriety of assigning the subject of this article to that genus. 



Locality. — The only specimen I have met with of this species is 

 the one represented in the plate. 



Explanation of Plate X. 



No. 1. Pycnodus liassicus, size of nature. 

 Nos. 2, 3. Front teeth, magnified. 

 Nos. 4, 5. Vomerine tritor, ditto. 

 No. 6. Nuchal scale, ditto. 



P. DE. M. Grey Egerton. 



July 7, 1853. 



