PANAMIC-PACIFIC PELECYPODA 257 



Distinguished from typical L. elenense by its wider shell and less flat- 

 tened dorsal-posterior area. This form constitutes a doubtful subspecies. It 

 occurs constantly with the typical form with which it appears to intergrade. 



I have specimens from the Pearl Islands and from Manta. 



Laeylcardiam clarlonense (Hertlein and Strong) Plate 39, figures 5, 5a 



Cardium (Laevicardium) clarionense Hertlein and Strong, 1947, Zoologica, vol. 31, pt. 

 4, pp. 144, 145, pi. 1, figs. 5, 6, 7, 14. 



Shell very obliquely ovate, rather compressed, pointed at the beaks, 

 very slightly gaping at the sides; smooth over most of the surface but with 

 fine radial sculpture along the basal margin and at the edges of the resting 

 stages, internally with the basal and lower half of the anterior margin finely 

 serrated; there is also a narrow posterior area defined by a slight angle 

 exteriorly but scarcely visible internally; exterior light yellowish, variously 

 maculated and spotted with brown, internally with a large yellow patch 

 extending from the beaks to the middle of the shell, a broad white band 

 along the margins; lateral teeth strong, cardinal teeth small, two in the left 

 valve, one in the right. The type measures: maximum vertical diameter, 

 31.4 mm., maximum longitudinal diameter, 23.9 mm,, convexity (both 

 valves), 16.5 mm. (Hertlem and Strong, 1947.) 



This species resembles L. elenense (Sowerby) by its external coloration 

 but is larger, narrower, and higher. According to Hertlein and Strong, the 

 largest specimen seen by them has a maximum height of 41 mm. A single 

 specimen collected by Mr. Stewart Jadis of the Panama Canal Zone, was 

 found at Palo Seco. This specimen measures: length 18 mm., height 20 mm., 

 diameter of closed valves 13.2 mm. 



Range — Gulf of California to Panama. Mexico: Santa Inez Bay; Gulf 

 of California; Clarion Island; Revillagigedo group, (all Hertlein and Strong). 

 Canal Zone: Palo Seco. 



Laevicardium elatnm (Sowerby) Plate 38, figures 1-lb 



Cardium elatum Sowerby, 1833, Proc. Zool. Soc. London, p. 84 Guaymas. — Sowerby, 

 1834, Conch. Illust., pi. 46, fig, 3.— Reeve, 1844, Conch. Icon., vol. 2, Cardium, 

 pi. 8, fig. 41 



Cardium {Laevicardium) elatum Sowerby, Hertlein and Strong, 1947, Zoologica, vol. 

 31, pt. 4, p. 145. 



Shell often large, oval, somewhat oblique, and convex. Surface smooth 

 and with numerous, shallow radial riblets, or grooves. Color white or yellow 

 covered with a thin brownish periostracum. Margins serrated and inter- 

 locking. 



This is the largest species of Cardium known, sometimes reaching a 

 height of five inches or more. A species of the Gulf of California; records as 

 far south as Panama are doubtful. 



Range — Gulf of California. 



Superfamily VENERACEA Menke, 1830 

 Family VENERIDAE Menke, 1830 



Marine clamlike pelecypods, the shell usually ovate-cordate to sub- 

 trigonal in shape, the valves similar in form and sculpture, porcellaneous, 

 the umbones generally prominent, ending in small, coiled or prosogyrate 



