250 AXEL A. OLSSON 



The Pacific shell is closely related to P. soleniformis Bruguiere (P. 

 hiatus Meuschen, nonbinomial) from the Caribbean, the two forms at 

 times indistinguishable. 



Range — Lower California to Ecuador. Panama Canal Zone: Venado 

 Beach. Ecuador: Manta; Santa Elena. 



Papyridea mantaensis, neiw species Plate 37, figures 5, 5a; 



Plate 38, figure 7 



Shell often large (length 64 mm.), elongate quadrate, subsolid and 

 strongly vaulted along the posterior-umbonal slope, depressed across the 

 anterior-middle zone. The beaks and umbones are decidedly anterior in posi- 

 tion, the posterior side hence much the longer, higher and wider. The riblets 

 are rather coarse (about 36 in number), unequal, trigonal in section, their 

 anterior side wider, the spaces between them grooved or narrowly flattened. 

 The riblets on the posterior-dorsal slope are largest, and often coarsely 

 squamose, and their ends cut the margins in deep serrations. Color generally 

 white mottled on the umbonal slope with pale red or violet spots. The 

 periostracum is a thin, ash-colored skin. Tip of beaks white or stained with 

 amber. 



Length 40.5 mm., height 29.5 mm., diameter 8.7 mm. (a left valve). 

 Manta, Ecuador. Holotype, ANSP 218895; paratype, ANSP 218896. 



This form although quite variable in its shape appears to be fully 

 distinct from P. soleniformis aspersa differing by its much heavier shell 

 which is usually strongly vaulted along the umbonal slope as well as by 

 its much stronger, elevated riblets. The surface color is generally a creamy 

 white, faintly mottled with small spots except the tip of the beaks which 

 may be more deeply colored. 



Range — Panama to northern Peru. Panama: Bucaro. Ecuador: Manta; 

 Santa Elena. Peru: Zorritos; Mancora. 



Subfamily FKAGmAE 

 Genus TRIGOiaOCARDIA Dall, 1900 



Type species by original designation, Cardium granijerum Broderip and 

 Sowerby. 



Shell small or of medium size, heavy, obliquely trigonal or squarely 

 cordate to rounded, with high umbones setoff by a sharp, posterior angula- 

 tion. Posterior side more or less smoothly flattened or mesially sulcated. 

 Anterior side rounded. Sculpture formed by strong ribs, their tops smooth, 

 beaded or covered by a deciduous layer formed of coarse, imbricated scales 

 which is destroyed by slight wear. Spaces between the ribs often strongly 

 cross-threaded or pitted. Hinge with the lateral teeth spaced equidistant 

 from the cardinals or with the anterior lateral tooth closer. 



The genus may be divided into three subgenera as follows. 



L Shells with the beaks and umbones subcentral. Posterior slope sub- 

 truncated, depressed, sometimes with a strong medial sulcation which 

 deeply emarginates the margin. Lateral teeth equisdistant from the 

 cardinals. 



