236 Lamarck's Genera of Shells. 



tion of the anus. The testacella is seldom met with alive, 

 living almost constantly buried in the ground, where it preys on 

 earth-worms. 



One Species. Testacella haliotidea *.' 



No farther description. South of France. PI. VII. Fig. 128. 



5. VlTRlNAt.- 



Body creeping, elongate, limacirorm,'"greatest part straight; 

 hinder part separate from the foot, spiral, and enveloped in a 

 Bhell. Several posterior appendages of*the mantle spread over 

 the shell, apparently for the purpose oft'.cleaning it, and partly 

 cover it. Four tentacula, the two anterior very short. Orifice 

 for respiration, and anus, very far bacl«,'()n the right side. 



Shell small, very thin, depressed, jferminated above by a 

 short spire ; last whorl very large. Aperture large, rounded- 

 oval ; left margin arched, slightly involate. 



The Vitrina is small, and frequents oi)6l, shady places. 



One Species. Vitrina pellucida I. ' 



No further description. France^ PI. VII. Fig. 129. 



« ' 

 Third Order. [.. 



Traciielipod^." 



Body spiral at the posterior part, which is separated from 

 the foot, and always enveloped in the/shell. Foot free, flat- 

 tened, attached to the inferior base of the neck, or the anterior 

 part of the body, and serves for creeping. Shell spirivalve, en- 

 sheathing. 



The trachelipoda differ from the gasteropoda, by the poste- 

 rior portion of the body being spirally'convolute, and by the 

 greater part of the foot being free, and only attached to the 

 inferior base of the neck, or fore-part of the body. The spiral 

 portion of the body never projects beyond the shell, its natural 

 conformation not allowing it to extend, itself in a straight line. 



All the trachelipoda are conchiferouS ; their shell, generally 

 external, is always mere or less spiral. '^ 



The genera and species cf this order are much more nume- 



• Like a JkaSo<i«. \ From litrum, glass. t Tiamparent. 



