232 AXEL A. OLSSON 



an external, partly obsolete, amphidectic tensilium and a larger, subumbonal 

 resilium. The scar of the resilium or resilifer is a narrow groove in 

 the middle of the hinge plate and lies directly behind the beaks. The hinge 

 plate is relatively narrow and carries strong, lateral teeth and sockets, the 

 posterior set more distant, the anterior small and adjacent; in the left valve, 

 the posterior lateral is an elongated lamina, the anterior lateral is a small, 

 short tooth, and adjacent, and behind it is a small pseudocardinal tooth. In 

 the right valve, the posterior lateral socket is large and conspicuous, its 

 lower rim enlarged and toothlike. The adductor scars are subequal in size, 

 placed rather high within, connected by an entire pallial line. The cavity 

 of shell within is smooth or punctate. 



Bornia is recognizable by its high, trigonal shape, its high, convex 

 umbones, its polished surface and strong hinge in which the lateral teeth 

 and sockets are most conspicuous. The species are probably parasitic or 

 commensal in habit, and where found, generally abundant. 



Bomla venada, new species Plate 35, figure 12 



Shell small, ovate or boat-shaped, convex, with nearly median umbone 

 and beak, white. The two ends of the valve are much alike in shape and 

 degree of roundness. The surface is smooth, polished, the lines of growth 

 fine except for a narrow band near the ventral margin marked with several 

 strong resting marks; in addition, the ventral margin is obscurely undulated. 

 Shell cavity deep, the adductor scars small, equal and placed high within 

 the valve. 



Length 9.1 mm., height 6.6 mm., diameter 2.4 mm. a left valve, Venado 

 Beach, Holotype, ANSP 218963. 



Recognized by its shape and obscure radial undulations along the 

 ventral margin. 



Range — Panama. Canal Zone: Venado Beach. 



Bomla egretta, new species Plate 35, figure 11 



The shell is relatively large, high-ovate, with narrow, pointed proso- 

 gyrate beaks placed slightly in front of the middle, the two ends of the 

 shell nearly alike and widely rounded, the surface mildly convex to flattened. 

 Surface smooth, polished, the lines of growth fine and hardly showing; 

 along the anterior and posterior-ventral corners, there are a few, low, ob^ 

 scure, radial ripples or undulations and these show best on the inner side 

 of the valve but the whole of the ventral margin is more or less weakly 

 undulated. The adductor scars are placed high within the cavity and sub- 

 equal in size, the pallial line entire but with waved or irregular borders. 



Length 10 mm., height 9.7 mm., diameter 2.1 mm. (a left valve). 

 Sechurita near Zorritos, Peru. Holotype, ANSP 218885. 



Only a single valve of this fine species is known to me. 

 Range — Peru. Peru: Sechurita, about 1 mile southwest of Zorritos. 

 Bomla zorritensls, new species Plate 35, figures 9, 9a 



Shell broadly trigonal or hatchet-shaped, subequilateral, with wide, 

 submedian umbones, the two sides of the shell similar, their dorsal margins 

 descending to a rounded end. Middle surface of disk wide, almost flattened, 



