146 GEOLOGICAL BIOLOGY. 



lariidae the genus Lamellaria is distributed in all three oceans 

 Atlantic, Pacific, and Indian. The three genera Velutina, 

 Marsenina, Oneidiopsis are confined to boreal seas, and the 

 fifth genus, Caledoniella, is from New Caledonia alone. 



In another family, the Cypraeidae, all the genera are ad- 

 justed to warm and temperate seas ; the principal genus, 

 Cypraea, of which more than a hundred and fifty species 

 have been described, is confined entirely to warm seas ; the 

 majority of the species are from the Indian Ocean and the 

 Australian and Polynesian oceans. This genus also dates 

 from as early as the Middle Mesozoic, species having been 

 found in the Jurassic, Cretaceous, and Tertiary rocks. Other 

 genera of the family live in the Mediterranean waters, and ex- 

 tend across to the shores of the West India islands and Cen- 

 tral America, and are also seen on the west coast of America. 



To select another family, outside the immediate suborder 

 we are now considering, in the Buccinidae we find as much of 

 an adaptation to cold waters as in the last case there was to 

 warm waters. 



The genera Buccinum and Siphonalia are distributed in 

 both boreal and austral seas ; Chrysodomus has a circumpolar 

 distribution ; Liomesus is only found in arctic and boreal 

 seas. Other genera of the same family are distributed in the 

 intermediate seas, both Atlantic and Pacific ; and several 

 genera which are associated by their structure in the same 

 family, as Phos Hindsia and Dipsaceus, are restricted to the 

 warmer seas about the Philippines, Indian, China, and Car- 

 ibbean shores, or the corresponding warmer western coasts of 

 America. 



This family dates back to as early as the Cretaceous 

 era. 



Tabulation of the Facts. — The following table expresses in 

 graphic form a summary for all Gastropods, of the facts re- 

 garding the actual present adjustment of the form and struc- 

 ture of these organisms (as expressed in the different classes, 

 orders, and families into which they are classified), and the 

 various conditions of environment (ranging from the abysses 

 of the ocean to the extremities of leaves of trees in the opea 

 air) in which they find their normal life habitat. 



