§36. CRUSTACEANS AND FISHES. 251 



limestone of Malta a species of Crab occurs in great per- 

 fection, as exemplified in the specimen before us (Lign. 43). 

 The minute crustaceans, termed Cy prides, which swarm in 

 our pools, lakes, and streams of fresh water, are abundantly 

 distributed in some of the tertiary fluviatile deposits.* 



Ligx. 43. — Fossil Crab, trom Malta — {half the natural size). 

 (Cancer Macrochelus.) 



Fishes of the Tertiary Epoch. The fishes that have 

 been collected from the various groups of tertiary strata, 

 comprise many hundred species, belonging to all the ex- 

 isting orders and families ; but some of the most ancient 

 forms either do not occur, or are but feebly represented. f 

 Nearly two hundred species are figured and described by 

 M. Agassiz in his splendid work on fossil fishes ; of which 

 between forty and fifty belong to the universally distri- 

 buted family, the Sharks. Teeth of various genera of this 

 voracious tribe, are found in abundance in numerous British 

 localities. J In the Crag, teeth of enormous size (Carcha- 

 rocloii) are often met with ; and the same species occurs in 

 the tertiary of Maryland. The teeth of several genera of 



* Medals of Creation, vol. ii. p. 119. 



f See Genealogical table of the class Fishes, in M. Agassiz's " Re- 

 cherehes sur les Poissons Fossiles.^ 

 J Medals of Creation, vol. ii. p. 623. 



