1 62 THE HISTORY OF CREATION. 



and also to the Cuttle-fish (through the Butterfly-snails). 

 The more highly developed Snails, with large heads 

 (Delocephala), can be divided into Snails with gills 

 (Branchiata) and Snails with lungs (Pulmonata). Among 

 the latter are the Land-snails, the only Molluscs which have 

 left the water and become habituated to a life on land. 

 The great majority of Snails live in the sea, only a few live 

 in fresh water. Some River-snails in the tropics (the 

 Ampullaria) are amphibious, living sometimes on land, 

 sometimes in water, and at one time they breathe through 

 gills, at another through lungs. They have both kinds of 

 respiratory organs, like the Mud-fish and Gilled Newts 

 among the Vertebrata. 



The fourth and last class, and at the same time the most 

 highly developed class of Molluscs, is that of the Cuttles, or 

 Poulps, also called Cephalopoda (foot attached to the head). 

 They all live in the sea, and are distinguished from Snails 

 by eight, ten, or more long arms, which surround the mouth 

 in a circle. The Cuttles existing in our recent oceans — the 

 Sepia, Calamary, Argonaut, and Pearly Nautilus — are, like 

 the few Spiral-gill Lamp-shells of the present time, but a 

 poor remnant of the host which represents this class in the 

 oceans of the primordial, primary, and secondary periods. 

 The numerous fossil " Ammon's horns " (Ammonites), " pearl 

 boats " (Nautilus), and " thunderbolts " (Belemnites) are evi- 

 dences of the long since extinct splendour of the tribe. 

 The Poulps, or Cuttles, have probably developed out of a 

 low branch of the snail class, out of the Butterfly-snails 

 (Pteropoda) or kindred forms. 



The diflerent sub-classes and orders, distinguished in the 

 four classes of Molluscs, whose systematic succession is 



