GASTEROPODA 73 



the shell is wanting or rudimentary, and small compared with 

 the bulk of the animal. A single species of the genus Cari- 

 naria has been found in the middle tertiary of Turin. 



StromMdce. — The Strombs with their massive shells, never- 

 theless, resemble the fragile Heteropods in some respects. 

 They have the same lingual dentition, and the same carnivo- 

 rous habits ; and though living on the sea-bed, they rather leap 

 than glide, having a narrow sole and a deeply-divided opercu- 

 ligerous lobe. Characteristic of the warmer zones of existing 

 seas, they are only found fossilized in the newer tertiary strata 

 of countries south of Britain ; but there is a group of little shells 

 related to the recent Strombus fissurcllus in the older tertiaries 

 of London, Paris, and America, to which Agassiz has given the 

 name Rimella. The allied genus of scorpion-shells (Ptcroccra), 

 now peculiar to eastern seas, has been described as occurring 

 fossil in the secondary strata of Europe ; but the extinct 

 species appear to be more nearly related to A'porrhais. This 

 genus, now confined to the western shores of Europe, occurs in 

 all the tertiaries, and is represented in the secondary rocks by 

 many remarkable forms. Some have been separated under 

 the name Alaria ; and to this group the so-called Pterocera 

 Bcntlcyi may perhaps be referred (fig. 18, 2). Rostcllaria and 

 Serapvi (or Terebellum), now peculiar to the Eed or eastern 

 seas, are conspicuous fossils of the European eocene, at which 

 time their range extended to America. Some of the ancient 

 Eostellarias have the outer lip enormously expanded, as in 

 the R. anvpla (Hiiypocrcna) of the London cla}^. In the oolites 

 and chalk there are slender fusiform shells {Spinigcra, d'Orb., 

 fig. 18, 1) with spines on the sides of the whirls, as in some 

 recent Ranellce. 



Muricidw. — The great family of whelks, by far the most 

 important group of living sea-shells, is scarcely of higher anti- 

 quity than the eocene tertiary. The Puvpuvina of the oolites 

 (fig. 18, 3), and Columhcllina of the chalk, are extinct genera, 



