LIFE. 499 



Britain ; in India, or the Continent of Asia, there are but two species 

 over fifteen feet long ; in Africa, but one ; in all America, but 

 three ; and in the whole world, not more than six ; and the length 

 of the largest does not exceed twenty-five feet. The number of 

 living species exceeding ten feet in length is only 16 or 18. 



The Galapagos Islands are strikingly Reptilian at the present 

 time. But they afford only four lizards, as many snakes, a turtle, 

 and a large tortoise. The largest of the lizards, an aquatic species 

 of the genus Amblyrhynchus (having feet, however, instead of pad- 

 dles), is but three to four feet long. 



If so large a number of species as above mentioned existed in 

 Britain and its vicinity during the age of Eeptiles, what should be 

 the estimate for the whole world at that time ? The question is a 

 good one for consideration, although no definite reply can be 

 looked for. 



The culmination of the age of Reptiles occurred in the era of the 

 Wealden. But, as in the case of Mollusks, the culmination of the 

 grand type does not imply a culmination of all its subdivisions. 

 There is no evidence that the inferior group of Snakes had begun 

 to exist ; and the Mesozoic species of Turtles are inferior in grade 

 to those of the Cenozoic and the present age. 



3. Progress in Cenozoic Features. 



1. Among Plants. — (a.) Angiosperms. — The introduction in the Cre- 

 taceous of the great class of Angiosperms, — that to which all our 

 common fruit and shade trees belong. 



(b.) Palms. — The introduction in the Cretaceous of the tribe of 

 Palms, — also eminent for its fruits and other useful products. 



2. Among Radiates. — The introduction of the modern tribe of reef- 

 forming Corals, the Astrseoid Corals, and also the normal style of 

 Echinoids, that is, those having only the normal number of vertical 

 series of plates (p. 160), instead of an excessive number; as exem- 

 plified in the Cidaris, and other groups of the age. 



3. Among Mollusks. — An increase in the number of modern genera 

 of Conchifers and G-asteropods, and a larger proportion than before 

 of siphonated G-asteropods (beaked univalves) and siphonated 

 Conchifers. 



Among modern genera the following begin in the Jurassic : — Rimula, Planor- 

 bis, Paludina, Jfelania, Nerita, Pteroeera, Rosiellaria ? , Fusus, Tellina, Corbis, 

 Anomia, etc. In the Cretaceous : — Neithea, Crassatella, Axinsea (Pectunculus), 

 Petricola, Venus, Oliva, Ovula, Cyprsea, Voluta, Turris (Pleurotoma), Busycon, 

 Pseudobuccinum, etc. 



