PANAMIC-PACIFIC PELECYPODA 311 



white or a light brown, usually with three or more wide rays of a darker 

 brown running across the umbones towards the ventral margin; the inner 

 circle of the lunule is brown and the escutcheon is marked alternately with 

 bars of brown and white. Interior white, the adductor scars large and round, 

 the pallial sinus small but distinct. The ventral margin is neatly crenulated 

 on the anterior side, much coarser on the posterior; the posterior margin 

 itself is smooth. 



Length 44.7 mm., height 38.7 mm., diameter 29.2 mm. Pedro Gonzales, 

 Pearl Islands. Holotype, ANSP 218904. 



This fine species appears to be widely distributed but scarce at all 

 places. At Esmeraldas, Ecuador, this species lives deeply buried amongst 

 large boulders and rocks in bars exposed at the time of lowest tides, and 

 is sometimes obtained by the natives digging for other clams. 



I take pleasure in naming this species for Mr. Lee Beil, formerly 

 stationed in the Canal Zone, an enthusiastic and careful collector of 

 Panama marine shells. 



Range — Panama southward to Ecuador. Panama: Pearl Islands; San 

 Carlos; Puerto Mensabi; Concepcion Beach near Poicri; Bucaro; Guanico. 

 Colombia: Isla del Gallo. Ecuador: Esmeraldas; Sua; Pedernales; Char- 

 apota; Manta; Manglaralto; Santa Elena. 



Genus COLOlfCHE, new genus 

 Type species, Colonche ecuadoriana, new species. 



The shell is broadly orbicular, with large, convex umbones ending in 

 small beaks placed nearer the anterior end. Surface color white, often chalky, 

 sculptured with fine, scabrous, radial riblets, stronger and coarser on the 

 anterior slope. The lunule and escutcheon are both absent, or the lunular 

 area may be weakly indicated by a slight change of sculpture. Hinge as in 

 Nioche, the right, anterior cardinal small and narrow, the right, middle, 

 anterior tooth, stout, bifid, and produced downward so as to form the 

 lower rim of the anterior socket. The pallial sinus is short but ample. 



Colonche differs principally from Nioche in the complete absence of 

 a lunule and an escutcheon. 



Colonche ecuadoriana, new species Plate 41, figure 2; 



Plate 55, figure 5 



Shell of medium size (length to about 50 mm.), ovate, subsolid, plurnp, 

 chalky white, the beaks strongly anterior in position, the posterior side 

 hence much longer, the greatest height of the valve is attained along a 

 line extending from the middle of the dorsal margin on the posterior side 

 across to the middle of the ventral. There is no lunule or escutcheon in 

 either valve. The surface is usually chalky and somewhat weathered but 

 when in more perfect condition shows a highly elaborate sculpture of many 

 small radial riblets or costals, closely noded by evenly spaced concentrics, 

 the resulting effect being sharp and harsh to the touch. On the earlier 

 part of the umbone, the riblets are at first simple but soon, one and later 

 many more interstitials appear in the interspaces and soon gaining in size 

 so that the resulting sculpture near the ventral side is uniform and resembles 

 that of a coarsely woven fabric but with the radial strands dominant; an- 



