340 AXEL A. OLSSON 



This species was figured by Reeve and Sowerby under the name 

 "cayennensis Lamarck" from specimens taken at Panama or Santa Elena, 

 but true D. cayennensis is generally believed to be a Caribbean species. 

 According to Hanley, the figure of D. cayennensis given by Delessert and 

 based on the original Lamarckian specimens, agrees so well with D. striata 

 that he would hardly venture to consider the species distinct. Hertlein and 

 Strong have identified this species with D. assimilis Hanley (described from 

 Panama) which has much the same outHne and color, but its description 

 mentions a tooth along the posterior margin as in D. dentiferus, a species 

 to which it was compared. 



This species is common at Panama and is harvested in considerable 

 quantity; often seen in the local markets. 



Range — Mexico to Ecuador. Nicaragua: Isla Encantada, Corinto 

 (Hertlein and Strong). Costa Rica: Culebra Bay, Cedro Island, Gulf of 

 Nicoya (Hertlein and Strong). Panama: Burica Peninsula; Concepcion 

 Beach at Poicri; El Lagartillo, Las Tables; Viveros and Gibraleon Islands, 

 Pearl Islands; Old Panama; Bella Vista; Isla del Gallo. Ecuador: Limones; 

 Indian kitchen middens on Rio Cayapas; Santa Elena. 



Donax mancorensis, new species Plate 61, figures 3-3b 



This shell is medium-sized, solid, trigonal, subquadrate, the anterior 

 side longer than the posterior, produced slightly at the end and rounded. 

 The umbones are convex or slightly humped producing a vaulted umbonal 

 slope which where it meets the ventral margin gives rise to a convex bulge. 

 In the adult, the surface is usually smooth and plain but with low flattened 

 radials showing under a glass except for a belt along the anterior umbonal 

 slope where there is also a weak cancellation and the lines in the interradial 

 grooves may result in small pits. There is a depressed or flattened lenticular 

 area in front of the beaks resembUng a smooth lunule without radials. Ex- 

 ternal color is mostly white or cream, the interior frequently stained with 

 purple. 



Length 25.4 mm., height 17.7 mm., diameter 13.3 mm. Zorritos, Peru. 

 Holotype, ANSP 218910. 



This species largely replaces D. peruvianus north of Cabo Blanco and 

 is common at Mancora and Zorritos. It is a shorter and more strongly 

 humped species than D. peruvianus. The sculpture is never as strongly 

 cancellated as in D. ecuadorianus. 



Range — Coast of northern Peru. Peru: Mancora; Zorritos. 



Donax ecuadorianus, new species Plate 61, figures 2-2b 



The shell is relatively small, solid, humped, trigonal, wedge-shaped, 

 and rather convex. The posterior side is short and sharply truncated, its 

 surface depressed or flattened; the anterior side is much lonjger, 

 narrowly rounded at the end with a low depressed zone just in front of 

 the posterior-umbonal angle. The sculpture is finely and neatly cancellated 

 over the whole surface formed by small, close-set, radial riblets, and a set 

 of sharply incised concentric lines; these lines are not strictly concentric 

 but over the middle of the disk, they appear to cross the riblets obliquely 

 forming deep pits in their interspaces and where the interspaces are wider 



