354 AXEL A. OLSSON 



Genus SOLECURTUS Blainville, 1824 

 (Solenocurtus Blainville emend., Psammosolen Risso, 1826) 



Type species by subsequent designation, Anton, 1839, S. strigilatuy 

 Blainville (r^Solen strigilatus Linne). 



Shell with broad, razor-shaped, rectangular valves, with the umbones 

 placed a little nearer the anterior end but never terminal, the ends rounded, 

 the posterior gap large. The surface is coarsely marked with growth lines 

 and generally with a series of transverse and obHque lines across the middle 

 and posterior parts of the disk. The pallial sinus is large and deep. 



Soleciirtus broggii Pilsbry ond Olsson Plate 63, figure 2 



Solecurtus broggii Pilsbry and Olsson, 1944, Proc. Acad. Nat. Sci. Philadelphia, vol. 



93, p. 71, pi. 18, fig. 4 Puerto Callo, Jipijapa, Ecuador, also in the Pliocene 



of Ecuador. — Hertlein and Strong, 1950, Zoologica, vol. 35, pt. 4, pp. 227, 228. — 



Keen, 1958, Sea Shells of Tropical West America, p. 191, fig. 468. 



The shell is large, coarse, moderately convex, its dorsal and ventral 

 margins nearly straight and parallel, the posterior gap large. The small beak 

 is placed a short distance behind the front third of the length. Surface 

 marked with coarse, irregular lines of growth except on the posterior area 

 where, in addition, there is a series of spaced lines which cross the shell 

 vertically and bend obliquely forward near their lower ends. There is also 

 one or more faint rays radiating from the umbones towards the ventral 

 margin. Coloration white and in life covered with a coarse, black perio- 

 stracum. 



Length 84 mm., height 33 mm., diameter of a valve 10.3 mm. 



Sparingly distributed along the coast of Ecuador and northern Peru. 

 It is locally common as a Pliocene fossil at Punta Blanca in Ecuador. 



Range — Panama southward to northern Peru. Panama: Gulf of Chiriqui 

 (Hertlein and Strong). Ecuador: Jaramijo; Puerto Callo. Peru: Zorritos, 

 Boca Pan; Punta Picos. 



Solecurtus guajmasensis (Lowe) Plate 63, figure 8 



Psammosolen guaymascnsis Lowe, 1935, Trans. San Diego Soc. Nat. Hist, vol. 8, No. 

 6, p. 18, pi. 1, fig. 7 Guayraas. — Strong and Hertlein, 1950, Zoologica, vol. 

 35, pt. 4, pp. 228, 229.— Keen, 1958, Sea Shells of Tropical West America, n. 

 192, fig. 469. 



This is a smaller, shorter species with the umbones in a more central 

 position. The oblique lines are developed over a larger part of the surface 

 and have been likened to that produced by a series of overlapping clap- 

 boards. 



Range — Lower California to Panama. Panama: Gulf of Chiriqui (Hert- 

 lein and Strong). 



Genus HETERODONAX Morch, 1853 

 Type species by monotypy, Tellina bimaculata Linne. 



Shell ovate, inequilateral, the beaks and umbones a little posterior of 

 the middle, hence the anterior side is longer, rounded at the end, the shorter 

 posterior side often appearing somewhat truncated. Ligament external, 

 seated on or behind a high nymphal plate. Hinge: left valve has a large, 



