226 NATURAL HISTORY. 



near their bases ; the foot is oblong. Sixteen living species have been described. They inhabit 

 deep water in the Red Sea, the Philippines, Japan, etc. 



Genus Rinyicula. Four species are found living in the Mediterranean, India, &c. 



Genus Tornatina. The shell has a conspicuous spire, fusiform or cylindrical ; suture channelled, 

 columella plaited; head of animal broad, rounded in front, with triangular tentacular lobes ; eyes at 

 their base ; foot truncated in front. Tornatina is found on sandy bottoms at a depth of thirty 

 fathoms. Fifteen species occur, very widely distributed over the world. 



FAMILY XXXVI. BTJLLID^E. 



The shell is thin, convoluted, cylindrical, or globular ; spire concealed, aperture long ; lip sharp, 

 without operculum. The shell is more or less internal, being covered by the 

 lobes of the mantle of the animal. The Bullidce are animal feeders ; the gizzard 

 is provided with calcareous plates, which assist in the process of digestion. 



Genus Bulla, the " Bubble-shell." The shell in Bulla has no spire ; the 

 aperture is as long as the shell, and rounded at the ends ; the tentacular lobes 

 form with the head a flattened disc, truncated in front, lobed behind. B^dla is 

 found living from low water to thirty fathoms. Fifty widely -distributed species 

 have been described. 



In the genus Scopliander * the characters are, shell convolute ; spire con- 

 cealed ; aperture expanded, oblong ; surface spirally striated ; animal blind ; 

 head oblong ; foot broad and short ; the lobes of the mantle partially envelop 

 BULLA OBLONGA. * ne shell. Five species occur recent, in Britain, Norway, the Mediterranean, 



&c., living at a depth of fifty fathoms. 



Genus Philine. The animal is like a Slug ; mantle entirely covering the shell ; head oblong ; 

 blind ; foot broad. It is found living in Britain, Norway, the West Indies, itc. 



The genus Doridium has only a rudimentary membranous shell, covered by the mantle. 

 The other remaining genus (Gastropteroii) is shell-less. 



FAMILY XXXVII. APLYSIADJE. 



Genus Aplysia, the "Sea-hare," has a long neck; the head has four tentacles, the inner pair ear- 

 like, with the eyes at their bases ; the shell is translucent, oblong, rudimentary ; it is covered by 

 the mantle. " The Sea-hares live chiefly on seaweed, but also devour 

 animal substances. They inhabit the laminarian zone. When 

 molested they discharge a violet fluid from the edge of the internal 



surface of the mantle." (Goodsir.) Fortv species are found 



x 



Britain, Norway, West Indies, &c. 



Genus Dolabella. The shell is triangular, hard, APLYSIA INCA. 



6HELLOFAP- w ith a curved apex. The animal is like Aplysia. 



LYSIAINCA. Twelve species are found living in the Mediterranean, Ceylon, Sandwich Islands, &c. 

 Genus Notarcus. The animal is shell-less. Four species are found in the Mediter- 

 ranean, Red Sea, and the West Indies. 



The genus Lobiger has the shell exposed on the middle of the back, covering the plume-like gill. 



FAMILY XXXVIII. PLEUROBRANCHID^E. 



In the genus Pleurobranchus f the shell is quite covered by the mantle ; it is large, slightly 

 convex and flexible, nucleus sub-spiral ; head with two grooved tentacles, eyes at their bases ; foot large, 

 separated from the mantle by a furrow ; a single gill is placed on the right side between the mantle 

 and the foot. Twenty species are met with living in Britain, Norway, and the Mediterranean, &c. 



Genus Umbrella. The "Chinese Umbrella-shell " has a small depressed Limpet-like shell, marked 

 by concentric lines of growth ; the animal has a very large foot, deeply notched in front ; the 

 tentacles are ear-shaped. Three species are found in the Mediterranean, &c. 



The genus Tylodina, of which there are three species living, is very like the preceding. It occurs 

 in the Mediterranean, Norway, &c. 



* Greek, scaphe, a boat, and amr, a man. t Greek, pleura, the side, and branchia, the gills. 



