268 THALASSOPHILA. 



This singular, slipper-shaped little shell reminds one in 

 form of Catillus or Grypta ; it is covered with an oliva- 

 ceous epidermis, and has no operculum. It is an inhabitant 

 of the fresh-water streams of one of the West-Indian 

 Islands. 



Sab-order THALASSOPHILA. 



Eyes sessile on the front part of the frontal disk formed 

 by the expanded tentacles. 



Auimal marine, or living in the vicinity of the sea. 



Fam. AMPHIBOLID^. 



Lingual membrane large, very broad, expanded, and long, 

 with a central space or line scarcely defined ; teeth nume- 

 rous, equal, similar, four-sided, rather longer than broad, in 

 straight cross lines, with a broad, rounded lobe, rather more 

 sinuous on the inner than on the outer side of its front edge. 

 Eyes sessile on the front part of the cephalic disk formed 

 by the expanded tentacles. Respiratory cavity closed, except 

 a small valvular opening on the right side ; a large gland 

 occupying the position of the gill. Sexes united. 



Operculum horny, oval, sub-spiral. 



Shell spiral, globose, umbilicated. 



The animals of this family inhabit the salt marshes near 

 the sea, the living shells having Scrjnihe sometimes attached 

 to them. They appear to respire the free air, the gill being 

 rudimentary, and the mantle-cavity nearly closed. In the 

 armature of the lingual membrane, they approach the Lim- 

 neeidm, and the form of the frontal disk seems to resemble 

 the head of the same family with the tentacles greatly ex- 



