464 AXEL A. OLSSON 



equlvalve, the right valve being larger and more convex, the left valve 

 smaller, flatter or only slightly convex. The anterior side is higher, wider 

 and its margin evenly rounded, the posterior side shorter, its margin 

 oblique, straight below but becoming produced and somewhat flexed above. 

 Dorsal margin nearly straight, the tip of the beaks rising in a short point 

 above it. Pallial sinus short, not reaching to a line drawn under the beak. 

 The texture of the shell is thin enough so that the pallial sinus and other 

 internal markings show through plainly along with those of the surface such 

 as growth lines, faint undulations arranged roughly in concentric bands, 

 and still smaller radial striations. Granulation is minute and visible only 

 under microscopic power, and arranged concentrically. The periostracum is 

 thin, light in color. 



Length 23 mm., height 18 mm., diameter 7.9 mm. El Lagartillo, Panama. 

 Holotype, ANSP 218951. 



In shape, this species resembles P. stearnsi (as figured by Dall) but is 

 higher and has a more produced posterior end. It is a smaller and thinner 

 species than P. alta. The granulations of the surface are minute and for 

 the most part difficult to see; they are arranged along concentric lines. Two 

 specimens were collected on the beach at El Lagartillo, Panama. 



Range — Panama. Panama: El Lagartillo. 



Subgenus ALBEffANUS Pilsbry and Olsson, 1935 

 Type species by original designation, Periploma (Albimanus) -penta- 



dactylus Pilsbry and Olsson. Panama. 



Shell small, strongly inequilateral and inequivalve, white, pearly and 



rather stout, longer than high, with five strong radial ribs which project 



like claws at the margin. Beaks not slit. 



Periploma (Albimanus) pentadactylns Pilsbry and Olsson Plate 82, figures 3, 3a 



Periploma {Albimanus) pentadactylns Pilsbry and Olsson, 1935, Nautilus, vol. 48, No. 

 4, pp. 118, 119, pi. 6, figs. 5, 6, 7. 



The shell is white, oblong, much longer than high, plump, conspicuously 

 inequivalve, the right valve strongly convex, the left valve weakly convex 

 to depressed and much smaller. In the right valve, the beak is placed close 

 to the posterior end which hence is short; below and behind the beak there 

 is a small, deeply sunken escutcheon bordered by a rib. The anterior-dorsal 

 margin is long and strongly arched, terminating in a point, the basal margin 

 trilobed. Sculpture is formed by strong, radial ribs, the second and fourth 

 bifid or seamed along the top, the third less distinctly so, the first 

 rib is simple, while the fifth and smallest rib bounds the escutcheon; these 

 ribs show in the interior and at the margin project as short, stout, clawlike 

 spurs. Delicate lines of growth are festooned between the ribs. The left valve 

 is much smaller than the right and with much weaker sculpture. 



Length 21.3 mm., height 15.3 mm., diameter 7 mm. (Type). 



The ribs begin when the shell is about 3 to 4 mm. long. It was found 

 in some abundance along the beach at Guanico. 

 Range — Panama. Panama: Guanico. 



Superfamily rOROJITACEA 

 Family CUSPIDAKIIDAE 

 Shell generally small, thin, corbuliform, mostly white or gray, rostrate 

 or pointed behind, the anterior side rounded and convex, with the umbones 



