PANAMIC-PACIFIC PELECYPODA 413 



often appearing banded, the deeper lines of the resting stages being spaced 

 some distance apart. Under a lens, the surface shows faint radial striae. 

 Patches of a thin, straw-colored periostracum may persist near the ventral 

 margin. Interior of the shell is a porcelain white and often so heavily 

 thickened that the pallial sinus and the adductor scars appear as if deeply 

 engraved. Adductor scars large, subequal, shiny. The pallial sinus is a large 

 bay, extending almost to the middle, its end obtusely rounded or angled, 

 its lower limb coalescent with the pallial line for about quarter of its 

 length. Cardinal teeth small, the anterior left and posterior right are double. 

 Length 85.2 mm., height 65 mm., diameter of a right valve 15 mm. 

 Mompiche, Ecuador. 



This is the largest and heaviest of the Panamic Macomas. 



Range — Panama to northern Peru, also Galapagos. Panama: Guanico. 

 Panama Canal Zone: Palo Seco. Colombia: Choco (Oscar Haught), USNM 

 488850. Ecuador: Limones; Mompiche; Sua; Pedernales; Charapota; Jara- 

 mijo. Peru: Tumbez. Galapagos: Tagus Cove and Charles Island (Tomlin). 



Psammotreta gubernacnla (Hanley) Plate 74, figures 4, 4a 



Tellina gubernaculum Hanley, 1844, Proc. Zool. Soc. London, p. 142. — Hanley, 1846, 



Thes. Icon., vol. 1, p. 325, No. 201, pi. 62, fig. 186 Real Lejos, Central America. 

 Macoma pads Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, vol. 84, p. 



95, pi. 10, figs. 1, la, 2, 3 La Paz, Lower California. 

 Macoma (Psammotreta) pads Pilsbry and Lowe, Hertlein and Strong, 1949, Zoologica, 



vol. 34, pt. 2, pp. 92, 93.— Hertlein and Strong, 1955, Bull. Amer. Mus. Nat. 



Hist., vol. 107, art. 2, p. 201. 



Shell subovate, inequilateral, the anterior side longer, broadly rounded 

 at the end, the posterior side short, depressed to mildly convex, the maxi- 

 mum inflation across the anterior-umbonal slope, flattened or weakly de- 

 pressed behind it. The valves are slightly unequal, the right a trifle larger, 

 the posterior flexure hardly noticeable except in the left valve. The dorsal 

 margin is slightly curved in front of the beaks, straight and more steeply 

 sloping behind them, the ventral margin moderately arcuate. The surface is 

 dull or polished, covered with fine, hardly visible growth lines and sometimes 

 extremely minute radial striae. Color plain white or shading into light, 

 ochraceous salmon towards the beaks, the same color within. The pallial 

 sinus is large, high, and angled in the middle, rounded at the end. Ligament 

 scar short, deeply inset into the hinge plate. 



Length 52.5 mm., height 41 mm., diameter 18 mm. Bella Vista, Panama 

 City, Panama. 



As noted by Pilsbry and Lowe (as pads), this species shows much 

 variation in shape, some shells are decidely more quadrate or oblong. It is 

 also similar to P. dombei, but it may be distinguished by its flatter and 

 less flexuous valves. 



Range — Lower California to Ecuador. Panama: Bella Vista beach, 

 Panama City; Puerto Chame; Bucaro. Ecuador: Santa Elena; Puerto 

 Limones. 



Psammotreta asthenodon (Pilsbry and Lowe) Plate 74, figures 1, la 



Apolymetis asthenodon Pilsbry and Lowe, 1932, Proc. Acad. Nat. Sci. Philadelphia, vol. 

 84, p. 96, pi. 11, figs. 1-3. 



