484 THE WONDERS OF GEOLOGY. Lect. V. 



In the ocean-bed of the chalk we find vestiges of all the 

 principal groups of existing marine organisms ; comprising 

 many genera of the Shark family — viz. species of Cestracion, 

 Acanthias, Lamna, Galeus, &c. ; with fishes related to the 

 Chimaera, Salmon, Smelt, Pike, Kay, &c. : in fact, the 

 leading types of the majority of the fishes that inhabit the 

 present seas,* The Cephalopoda and Echinodermata or 

 Sea-urchins, were profusely developed ; Star-fishes, En- 

 crinites, and other Radiaria ; crustaceans allied to the Crab, 

 Lobster, Shrimp, Prawn, &c. ; univalve and bivalve mol- 

 lusca ; and innumerable multitudes of Foraminifera ; — all 

 these forms of animal existence have left enduring memo- 

 rials of their presence in the seas of those remote ages. 

 And although we have likewise proof that numerous 

 extinct genera, together with others now of excessive 

 rarity, swarmed in prodigious numbers in the cretaceous 

 ocean ; and negative evidence that the Cetacea, as the 

 Whale, Porpoise, Seal, &c, were not among its inhabit- 

 ants, yet the diversified types of animated beings whose 

 relics are entombed in these strata, show that the waters of 

 the deep possessed the same general conditions, and main- 

 tained the same relations with the atmosphere and with 

 light, as at the present time. 



The most remarkable peculiarity in the zoological features 

 of the Chalk, relates to the predominance of Reptiles ; for, 

 with the single exception of a lizard belonging to the 

 family of the Iguanidce, which inhabits certain parts of 

 the sea-coasts of South America,! the Chelonians or 

 Turtles, are the only known existing marine animals of 

 this class. But the cretaceous sea was tenanted by several 

 saurians of considerable magnitude; namely, the Mosa- 



* See the chronological table in 1£ Agas^iz's Kecherchcs Bur les 

 Toissons Fossiles, tome i. 



f The Arnblyrhynchus crtstatus of the Galapagos Islands: Bee Mr. 

 Darwin's Journal, in the Colonial Library, p. 



