GASTEROPODA. 



203 



very accurately known any more than their internal struc- 

 ture. The eggs of the Pterotrachcea are very often seen 

 in a fine long band, like a thin thread, hanging to their 

 kernel. The Atlantacea apparently form a connecting 

 link with the Pteropoda. 



Family 1. — NUCLE OB RAN CHI A TA. 



Body naked, with a protuberance, kernel, or nucleus 

 on the back, in which the liver, &c. are contained; on 

 this are placed the gills, which consist of feathered, or 

 conical lobes, and are in some genera covered by a shell ; 

 underneath the body there is a nearly circular fin. 



Carinaria. Lam. — Shell glassy, transparent, very 

 thin, conical, flat at the sides, keeled, and having the apex 

 recurved; serving as a covering to the 

 gills. Animal, body long, fusiform ; head 

 distinct, on the base of which are two 

 long thread-like tentacula, on which the 

 eyes are placed ; the nucleus is stalked, and covered by 

 the shell; the tongue has in the middle line a three- 

 pointed tooth, and on each side three long hook-shaped 

 teeth. — 5 species. 



The three best known species of this singular genus, 

 are Carinaria vitrea, so called from its resemblance in 

 substance to glass, found in the African seas, where it is 

 very rare ; Carinaria fragilis, which is extremely delicate 

 in its texture, and inhabits the Mediterranean ; and Cari- 

 naria cymbium, or boat-shaped Carinaria, which is not 

 larger than a grain of sand, and can only be seen with 

 the assistance of a microscope, brought from the Eastern 

 Ocean and Mediterranean Sea; it is found on the coast 

 near Nice, and feeds on small Medusae and other gelatinous 

 substances, as also on minute fish, and occasionally the 

 more feeble of its own species. 



