S44 AXEL A. OLSSON 



median deeper groove and tooth at the margin. Color usually white tinged 

 with pink or purple. 



Variable in size; large specimens from Tumbez have a length of 42 mm., 

 and height of 34 mm. These specimens have a high, solid shell with gibbous 

 umbones. Fresh shells have a thin epidermis. 



Range — Gulf of California to Peru. For Mexican and Costa Rican 

 localities see Hertlein and Strong. Panama: San Carlos; El Lagartillo; 

 Guanico; Burica Peninsula; Pearl Islands. Colombia: Isla del Gallo. 

 Ecuador: Sua; San Francisco. Peru: Tumbez. 



Donax dentiferus Hanley Plate 59, figures 2-2b; 



Plate 85, figure 4 



Donax dentifera Hanley, 1843, Proc. Zool. Soc. London, pt. 11, p. 6. Hab. -- ? — Reeve, 



1854, Conch. Icon., vol. 8, Donax, pi. 1, figs. 2a, 2b. 

 Donax dentiferus Hanley, Sowerby, 1866, Thes. Conch., vol. 3, Donax, p. 307, No. 17, 



pi. 280, fig. 23. 

 Donax paytensis d'Orbigny, 1846, Voy. Amer. Merid., vol. 5, Mollusques, p. 541, 



unfigured. 



Similar to D. asper in shape but smaller and less convex, the beaks 

 placed a Httle more posteriorly, the umbones lower and flatter. The posterior 

 side is truncated, flattened, its sculpture divided unequally into two sections 

 by a submedian groove which ends in a double tooth at the margin. The 

 principal surface of the valves is sculptured with low, flat, smooth, radial 

 riblets separated by simple lines, coarse and somewhat cancellated near 

 the posterior keel and on the posterior slope. Color varies from pure white 

 through shades of pink, brown to dark purple, the interior often stained 

 a deep purple. The margins of the valves are crenulated, more coarsely so at 

 the posterior-ventral angle. 



An average specimen measures: length 34 mm., height 26 mm., 

 diameter 16.2 mm. 



This species is easily recognized by its high, trigonal shape, and especi- 

 ally by the strong, toothlike projection along the posterior margin formed 

 by a deep, medial, structural groove, often ending in a double tooth. D. 

 paytensis d'Orbigny, from Paita, Peru, is equivalent to D. dentiferus, as 

 shown by an examination of the type in the British Museum (Nat. Hist.) 

 D. assimilis Hanley, described from Panama, from its figure in Reeve, ap- 

 pears similar to D. dentiferus but has a longer and thinner shell. 



Range — Panama to Peru. Panama: Bucaro; Guanico; Puerto Mensabi. 

 Ecuador: Montanita; Canoa; Charapota; Sua. Peru: Paita (d'Orbigny as 

 paytensis). 



Donax obesus d'Orbigny Plate 61, figure 5; 



Plate 85, figure 3 



Donax obesa d'Orbigny, 1846, Voy. Amer. Merid., vol. 5. Mollusques, p. 541, pi. 81, figs. 



28-30 Paita.— Reeve, 1854, Conch. Icon., vol. 8, Donax, pi. 7, fig. 49. 

 Donax obesus d'Orbigny, Sowerby, 1866, Thes. Conch., vol. 3, Donax, p. 310, pi. 281, 



figs. 42, 43. 



Shell small, short, ovately trigonal in shape, plump or convex, with 

 wide umbones placed a little posterior of the middle line. The posterior 

 side is high, subtruncated or widely rounded at the end, without an angled 

 umbonal slope; the anterior side is a little longer, its dorsal margin sloping 



