LEPETID.T:. 67 



Genus LEPETA Gray, 1847. 



Shell patelliform, the embryonic nucleus spiral, lost in the adult ; 

 apex in front of the middle ; no internal septum. Animal without 

 external branchiae ; having the muzzle produced into a labial 

 process on each side. Dental formula 2'O1'02, the uncini narrow, 

 erect, provided with cusps. Type, L. cceca. 



Section Lepeta s. str. Apex erect ; anterior terminations of the 

 great muscle-scar in front of the apex. Color whitish or light-brown. 

 Surface granulate. Apex of rhachidian tooth 5-cu?pidate, middle 

 cusp large, lateral cusps small ; uncini subspatulate at apex, obtuse, 

 not ciliated. 



Section Cryptobranchia Midd. Ape^: inclined forward, the 

 anterior terminations of the muscle-scar not in front of it. Surface 

 not granulate ; color whitish. Apex of rhachidian tooth tricuspi- 

 date, the cusps nearly equal ; uncini spatulate. Type, C. concentrica. 



Subgenus PILIDIUM Forbes. 



Apex of shell anterior ; surface delicately radiately ribbed and 

 granulate ; color dark orange or reddish. 



Apex of rhachidian tooth tricuspidate, the middle cusp much the 

 -t, side cusps small, triangular, disjoined from the central one 

 at their bases ; uncini elongated, apex lanceolate, its inner margin 

 densely ciliate. 



Genus PROPILIDIUM Forbes & Hanley, 1849. 



Shell patelliform, elevated ; the spiral nucleus retained in the 

 adult ; apex central ; surface cancellated ; inside having a small tri- 

 angular plate situated deep in the cavity, as in Puncturella. Type, 

 P. ancyloide. 



Rhachidian tooth tricuspidate, the central cusp rather long, sidei_ 

 cusps small, separated from the middle cusp at their bases. Uncini 

 with the cusps finely denticulated. 



Subfamily LEPETELLIX^E Ball. 



Radula having three teeth on each side of the simple central 

 tooth. 



Genus LEPETELLA Yerrill, 1880. 



Shell patelliform, small, smooth, oval, conical, with a subcentral 

 apex, spiral in the young. Animal having distinct eyes. Radula 

 having lateral teeth and uncini, formula 2'1'1'1'2. Type, L. tubi- 

 cola. 



