92 PALAEONTOLOGY. 



fossils of an earlier period than that in which the last group 

 began to nourish. The carnivorous Naticidce and Pyramidd- 

 lidce are represented in the palaeozoic strata by Naticopsis, 

 Loxonema (fig. 26, i), and Macrocheilus (fig. 26, 2) ; most of the 

 species of the latter genus from the coal-measures of Ohio and 

 Illinois are more ventricose than the one figured from the 

 Devonian bed in Germany. The oceanic violet-snail (lan- 

 thina), so unlike any other existing shell-fish, seems related to 

 the Silurian Scalites, Raphistoma, and Holopea. Shells like 

 Scalaria and Solarium occur in the trias and oolites associated 

 with Chemnitzice (?) of extraordinary size, and species of 

 Eulima and Niso. These families of shells and the Ceri- 

 thiadce are more abundant fossil than recent, the known 

 numbers being 1500 extinct and 900 living forms. Solaria?, 

 with disconnected whorls and pyramidal opercula (Bifrontia, 

 Dh.), are common in the eocene tertiary, and a single living 

 species (B. zanclcea) has been discovered by M* Andrew. 



Amongst the tertiary Naticas are many with an oblique 

 aperture and peculiar perforation {Globulus, J. Shy. ^Ampul- 

 Una, BL) and others with prominences on the pillar (Deshaye- 

 sia, fig. 28, 6). The Nerinaias of the oolites are remarkable for 

 the spiral ridges (like the "worm" of a screw) winding round 

 their interior, and giving rise to the variety of singular pat- 

 terns seen in sections (fig. 27, 4). A similar structure exists 

 in the recent " telescope-shell" (Terebralia). The fresh-wi.ter 

 univalves of the Wealden and older tertiaries differ but little 

 from their recent congeners of the genera Paludina, Potamides, 

 Melania, and Melanopsis. Fossil Turritellw are of doubtful 

 occurrence before the tertiary; the Silurian species have the 

 peristome complete (Holopella, M'C.) ; another form (Proto, 

 fig. 28, 7) is characteristic of the miocene. Fossil Trochidce 

 are very numerous, but hitherto many Litorinidce have 

 doubtless been included with them. Perhaps no true Turbo 

 is known from strata before the cretaceous. 



