PANAMIC-PACIFIC PELECYPODA 249 



Shell broadly subelliptical, the valves slightly flexed, gaping at both 

 ends, vi^ith the umbones and beaks anterior of the middle, the posterior 

 side hence longer than the anterior and with the dorsal and ventral margins 

 nearly parallel. Hinge has a single large cardinal tooth in each valve, the 

 second cardinal tooth small or subobsolete, the lateral teeth strong and 

 equidistant. Ligament external, placed on the dorsal edge of a large, nymphal 

 plate. Sculpture composed of numerous, flattened or triangular ribs which 

 are larger and coarser on the posterior side. Posterior margin of valves 

 deeply serrated by the ends of the ribs. 



Papyridea crockeri (Strong and Hertlein) Plate 38, figures 5-5b 



Cardium {Papyridca) crockeri Strong and Hertlein, 1937, Proc. California Acad. Sci., 

 ser. 4, vol. 22, No. 6, pp. 161, 162, pi. 34, figs. 1, 2, 7, 10. 



Shell ovate, a Httle longer than high, beaks nearly central; posterior 

 gap distinct; anterior-dorsal margin with a narrow depressed area; sculp- 

 tured with 48 low, flattened, radiating ribs with much narrower interspaces, 

 strongest at the posterior end, becoming narrower toward the anterior; of 

 these ribs 12 on the posterior end and 18 on the anterior end are imbricated 

 by small, pointed folds, more or less worn off towards the beaks, central 

 ribs smooth; exterior yellowish white with short patches of red arranged in 

 irregular concentric zones on the ribs; interior white stained with reddish 

 toward the beak on the anterior side; margins crenulated; ligament ex- 

 ternal, strong; hinge with one cardinal and two laterals in each valve. The 

 type measures: length, 46.8 mm., height, 41 mm., thickness of the two 

 valves, 29 mm. 



This species differs from Cardium (Papyridea) aspersu-m Sowerby in 

 possessing a more convex shell, which has a more rounded outline and it 

 is ornamented by brighter colors. The anterior plate on the hinge, which 

 bears a groove and lateral tooth, is longer than the corresponding plate in 

 P. aspersum. 



Off Cabo Tosco, Santa Margarita Island, Lower California, Mexico. 

 (Strong and Hertlein, 1937.) 



Papyridea solenilormls aspersa (Sowerby) Plate 37, figure 8; 



Plate 38, figures 6-6b; Plate 86, figure 7 



Cardium aspersum Sowerby, 1833, Proc. Zool. Soc. London, p. 85. Hab. ad Sanctam 



Elenam et ad Monten Christe.— Sowerby, 1834, Conch. Illust., Cardium, pi. 48, 



fig. 15. 

 Cardium {Papyridea) aspersum Sowerby, Hertlein and Strong, 1947, Zoologica, vol. 31, 



pt. 4, p. 139. 

 Cardium {Papyridea) spinosum var. aspersum Sowerby, Dall, 1900, Trans. Wagner Free 



Institute of Sciences, vol. 3, pt. 5, p. 1108. 



Shell broadly subovate, the low umbones and beaks anterior of the 

 middle, the posterior side somewhat longer and narrower, the two ends 

 subequal, slightly but evenly convex, the umbonal slope not noticeably 

 vaulted. Texture of shell relatively thin. Riblets numerous, smooth and 

 low, rounded or flattened in the middle zone and on the umbones and 

 separated by narrow, threaded interspaces; the anterior riblets heavier 

 and slightly noded; the posterior ones wider and scaly. Surface mottled 

 with violet red or reddish brown, heaviest on the umbones. 



Length 44 mm., height 34 mm., diameter 21.7 mm. Venado Beach, 

 Canal Zone. 



