444 AXEL A. OLSSON 



Shell elongate, reaching a length of nearly 5 inches but usually smaller, 

 white, thin to moderately solid, gaping slightly at both ends. Beaks and 

 umbones placed near the anterior one-fourth or one-fifth, the dorsal margins 

 at this point rolled over the beaks to form a wide, umbonal reflection which 

 is coarsely septate underneath, and anteriorly, under the whole, there is a 

 deep, umbilical perforation. The sculpture is produced by concentrically 

 frilled ridges, the frills, spaced evenly, forming a series of coarse, fluted, 

 or scabrously serrated, radial riblets. 



Closely related to the East American P. campechiensis, it is separated 

 by its average shorter, stouter shell, much coarser sculpture and by the 

 smaller perforation under the rolled-over, anterior-dorsal margin. 



Range — Mexico southward to Chile. Panama: Burica Peninsula; Bucaro. 

 Ecuador: Bahia de Canoa; Manta; Punta Blanca; Manglaralto; Santa Elena. 

 Peru: Tumbez; Boca Pan; Lobitos. 



Genus BARNEA Risso, 1826 



Type species by monotypy, Barnea spinosa Risso (== Pholas Candida 

 Linne). Recent, European seas. 



Like Pholas, the shell is elongate, subcylindrical in shape, thin, white, 

 but with a single accessory plate (protoplax), lanceolate in shape, and the 

 space below the umbonal reflection is open (not septate). The sculpture 

 is formed by imbricated, sharp, rasplike radial ribs which because of the 

 light weight of the shell show internally as pitted furrows. Pallial sinus is 

 usually well marked and of medium size and depth. 



Two subgenera are distinguishable. 



I. Anterior side rounded. 



Barnea, s.s. 



II. Anterior side narrowed into a beak. 



Anchomasa Leach 



Barnea (Anchomasa) snbtrnncata (Sowerby) Plate 78, figures 2-2c 



Pholas suhtruncata Sowerby, 1834, Proc. Zool. Soc. London, p. 69 "Isia la Plata." 

 Barnea pacifica Stearns, 1871, Conch. Memoranda, No. 7, p. 1. — Stearns, 1873, Proc. 



California Acad. Sci., vol. 5, p. 81, pi. 1, figs. 6, 6a-c. — Hertlein and Strong, 



1950, Zoologica, vol. 35, pt. 4. No. 19, p. 248. 

 Barnea {Anchomasa) suhtruncata (Sowerby), Turner, 1954, Johnsonia, vol. 3, No. 



33*, pp. 31-34, pis. 8 and 14 to 16. 



Shell subcylindrical, the dorsal and ventral sides parallel, convex and 

 thin, widely gaping at both ends, the anterior side shortened and produced 

 into a beak, the posterior side sharply truncated as if cut off. Length of 

 full grown shell is nearly 70 mm., but the average size is between 40 and 50 

 mm. Sculpture is formed by small, finely scabrous ribs which slowly diminish 

 in size posteriorly and in the Peruvian specimens do not fade out completely 

 except on the posterior dorsal slope. Apophyses long and narrow. 



This is a widely distributed species. It was found in large numbers on 

 the mudflat at the mouth of the Tumbez River in Peru. 



Range — Oregon to Chile (according to authors). Ecuador: Isla la 

 Plate (type locality). Peru: Tumbez; Paita. 



Genus CTRTOPIEURA Tryon, 1862 

 Type species by subsequent designation, Stoliczka, 1870, Pholas crucifera 

 Sowerby (= Pholas cruciger Sowerby). Ecuador. 



