MUSEUM OF COMPARATIVE ZOOLOGY. 367 



ELASMOGNATHA. 



Omalonyx, D'Orb. {Pelta, Beck.) Animal limaciform, blunt before, 



short behind : tentacles simple : mantle large, central, its margins holJing the 

 edges of the external shell : no longitudinal furrows above the margin of the 

 foot, and no caudal mucus pore : no distinct locomotive disk : external respi- 

 ratory and anal orifices on the right central margin of the mantle : generative 

 orifice below and behind the right eye-peduncle. 



Shell external, its margins imbedded in the mantle, rudimentary, non-spiral, 

 oval, depressed, unguiform. 



Jaw smooth, with median projection and accessory quadrate plate. 



Lingual memljrane with tricuspid centrals, tricuspid laterals, and multifid 

 quadrate marginals. 



West Indies and Brazil. 



For figure of animal and shell, see Genera of Recent Mollusca ; for jaw and 

 lingual dentition, see Heynemann, Malak, Blatt., 1868. 



Hyalimaz, H. & A. Ad. Animal limaciform, swollen at centre, blunt 

 before, and tapering behind : tentacles simple : mantle large, central, conceal- 

 ing all but a small opening, an internal .shell-plate : no longitudinal furrows 

 above the margin of the foot, and no caudal mucus pore : no distinct locomo- 

 tive disk : external respiratory and anal orifices on the central right margin of 

 •the mantle: orifice of combined genital system on right side of head, half-way 

 between eye-peduncle and mantle. 



Shell large, rudimentary, thin, oval, unguiform, non-spiral. 



Jaw smooth, with blunt median projection and accessory quadrate plate. 



Lingual membrane with tricuspid central teeth, multifid laterals, and quad- 

 rate marginals. 



Mauritius. 



For figure of animal, shell, jaw, and lingual dentition, see Fischer, Joum. de 

 Conch., XV. 218, PL X. 



Specimens from Mauritius examined by myself have the opening in the 

 mantle, which was not noticed by Fischer. 



Athoracophorus, Gould. {Janella, Gray ; Aneitea, Gray ; AneUeum, 

 McDon.; Triblniophonis, Humbert.) Animal limaciform, .subcylindrical, 

 tapering behind : tentacles wanting : mantle anterior, small, triangular, lateral, 

 adherent, enclosing one or more shell grains or plates : no longitudinal furrows 

 above the margin of the foot, and no caudal mucus pore ; no distinct locomotive 

 disk: external respiratory and anal orifices on the right central margin of the 

 mantle: orifice of combined genital system behind and below the right eye- 

 peduncle. 



Shell-plate internal, flat, calcareous, oblong, sometimes in separate grains. 



Jaw smooth, with median projection and quadrate accessory plate. 



Lingual membrane with peculiarly shaped teeth, with long, narrow, curving 

 base of attachment, and low, transverse, multifid cusp. 



