248 AXEL A. OLSSON 



a rule larger than those from more northerly stations. The shell varies con- 

 siderably in shape and in numbers of its ribs and it is possible that several 

 subspecies or geographic races should be recognized. This cockle is gathered 

 by the Peruvian fisherman both for bait and food. As a fossil, it is found 

 in the Pliocene of Ecuador and in the Pleistocene of Panama and Lower 

 California. 



Range — Gulf of California southward to Chile. Panama: Pearl Islands. 

 Ecuador: Santa Elena; Manta; Esmeraldas. Peru: Tumbez; Zorritos; Man- 

 cora; Negritos; Paita; Sechura; Lobos de Tierra; Bahia de la Independencia. 



Genus ACROSTERIGMA Dall, 1900 



Type species by original designation, Cardium dalli Heilprin. Pliocene 

 of Florida. 



Shell of medium or large size, elongate ovate, slightly oblique, the 

 height greater than the length. Umbones rather narrow, low, with small 

 beaks. Ribs round or flat, close-set, their interspaces an incised line or 

 groove only, except posteriorly where they are wider. The surface of the 

 ribs are smooth except the anterior ones which are nodosely wrinkled or 

 fringed with scales on the sides. Hinge with the anterior lateral tooth strong 

 and distant, the posterior one small and sometimes obsolete. The type 

 species has an internal rib in the middle of the umbonal cavity; it is lacking 

 in A. pristipleura Dall. 



Acrosterlgma pristlplenra (Dall) Plate 37, figure 7 



Cardium maculosum Sowerby, 1833, Proc. Zool. Soc. London, p. 85. (Not Cardium 



maculosum Wood, 1815). 

 Cardium maculatum Sowerby, 1840, Conch. Illust., Cardium, p. 4, No. 56, fig. 18. (Altered 



from maculosum, preoccupied). — Reeve, 1844, Conch. Icon., vol. 2, Cardium, pi. 



11, fig. 58. (Not C. maculatum Gmelin). 

 Cardium {Tr achy cardium) pristipleura Dall, 1901, Proc. U. S. Nat. Museum, vol. 23, 



p. 389. (New name for C. maculatum Sowerby, not Gmelin). 

 Cardium (Trachycardium) hornelli Tomlin, 1928, Jour. Conch., vol. 18, No. 7, p. 194. 



(Name proposed to replace C. maculatum Sowerby, preoccupied). 

 Cardium {Acrosterigma) pristipleura Dall, Hertlein and Strong, 1947, Zoologica, vol. 



31, pt. 4, p. 147. 



Valves are gently convex with the umbones narrowing gradually towards 

 the small beaks. Ribs number about 35; these are flattened and spaced so 

 close together that their flattened summiits seem to slightly overhang the 

 deeply incised interspaces between them. Surface of ribs smooth, except 

 the anterior set which are finely wrinkled and nodose. External color yel- 

 lowish white, flushed with purple, red or brown. 



Length 55.4 mm., height 7L5 mm., diameter 40.8 mm. Manta, Ecuador. 



This species is related to C. dalli Heilprin from the Pliocene of Florida, 

 but is smaller and lacks the internal subumbonal rib. 



Range — Gulf of California to Ecuador. Panama: Burica Peninsula. 

 Colombia: Gorgona Island (Tomlin). Ecuador: Manta; Isla la Plata. 



Genus PAPTREDEA Swainson, 1840 



Type species by subsequent designation, Gray, 1847, Cardium solenp- 

 forme Brugui^re, (Cardium hiatus Meuschen, 1787). 



