PANAMIC-PACIFIC PELECYPODA 403 



and on the sides of the beak. Surface of disk smooth and often polished 

 with fine growth line markings. Hinge teeth strong. The pallial sinus is 

 large and deep, and fills most of the interior cavity, highest under the 

 beak and from thence descending along an irregular line almost to the 

 anterior adductor scar, its lower limb fully confluent with the pallial line. 

 Adductor scars large, irregular in shape, and deeply impressed. An average 

 shell measures: Length 24.3 mm., height 14.1 mm., semidiameter 3.6 mm., 

 a right valve. 



An elegant species recognized by its relatively large size, solid, porcel- 

 laneous white shell generally suffused with rose-red on the umbones, along 

 the dorsal margins and in the interior. The posterior side is straight, nar- 

 rowed, and pointed at the end and slightly flexed. The species is abundant 

 at many localities, particularly at Old Panama and Balboa. 



Range — Lower California to Panama. Panama: Numerous localities. 



Moerella (Moerella) tambezensis, new species Plate 68, figure 5; 



Plate 69, figure 8 



Shell ovate-quadrate, its height nearly three-fifths of its length, of 

 medium convexity, thin and delicate, and of a white or pale pink color. The 

 beaks are small, placed near the anterior two-thirds, the posterior side 

 short, its margins descending, arcuate, the posterior slope itself flattened, 

 setoff from the shell disk by a rounded umbonal angle and a slight 

 change in sculpture. The ventral margin is slightly rounded passing into 

 the more rounded outline of the anterior margm. There is no lunule and 

 escutcheon. 1 he ventral margins are weakly impressed in the posterior 

 half with the result that the anterior margin appears to have a slight gap. 

 Surface is nearly smooth, marked only with weak growth incrementals which 

 are uniformly developed over the whole surface except on the pos- 

 terior slope where only the heavier incrementals generally persist. The 

 surface of the posterior area is also marked with small, divaricate, radial 

 striae which begin at the umbonal angle and radiate downward. Pallial 

 sinus ample, highest under the beak and then descending, its end not reach- 

 ing the anterior adductor but is placed low so that the lower limb of the 

 sinus is confluent with the pallial line for its whole length. Hinge normal, 

 the right valve with a large, bifid posterior cardinal tooth. 



Length 28.2 mm., height 18 mm., semidiameter 4.3., a right valve, 

 Tumbez, Peru. Holotype, ANSP 218940. 



On the mud flats at the mouth of the Tumbez River, Peru. 

 Range — Shores of the Gulf of Guayaquil, Ecuador and Peru. Ecuador: 

 Posorja. Peru: Tumbez. 



Moerella (Moerella) fellx (Hanley) Plate 69, figures 6, 6a 



Tellina felix Hanley, 1844, Proc. Zool. Soc. London, p. 71 "Panama." — Hanley, 18*6, 



Thes. Conch., vol. 1, Tellina, p. 281, pi. 57, fig. 52.— Maxwell Smith, 19+4, 



Panamic Marine Shells, p. 64, fig. 839. 

 Tellina (Moerella) felix Hanley, Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 2, 



No. 9, p. 70, pi. 1, fig. 1. 

 Tellina {Angulus) macneilii Dall, 1900, Proc. U. S. Nat. Museum, vol. 23, No. 1210, 



pp. 303, 318, pi. 3, fig. 7 (Guaymas). 

 Tellina {Moerella) macneilii Dall, Hertlein and Strong, 1949, Zoologica, vol. 34, pt. 



2, pp. 70, 71. 



Shell small (average length about 15 mm.), broadly elongate, rose-red, 

 more or less concentrically banded, equivalve, depressed or slightly convex. 



