MUSEUM OF COMPARATIVE ZOOLOGY. 367 
ELASMOGNATHA. 
Omalonyx, D’Ors. (Pelta, Beck.) Animal limaciform, blunt before, 
short behind ; tentacles simple : mantle large, central, its margins holding 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 membrane 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. 
Hyalimax, H. & A. Ap. 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, Journ. 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 ; Aneiteum, 
MeDon.; Tribiniophorus, 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 plato. 
Lingual membrane with peculiarly shaped teeth, with long, narrow, eurving 
base of attachment, and low, transverse, multifid cusp. 
