LEPETID.E. 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 2'01'02, 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-cuspidate, middle 

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

 not ciliated. 



Section Cryptobranchia Midd. Apex 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, (7. 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 

 largest, 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, side 

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

 with the cusps finely denticulated. 



Subfamily LEPETELLIN^: Dall. 



Radula having three teeth on each side of the simple central 

 tooth. 



Genus LEPETELLA Verrill, 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. 



