126 AXEL A. OLSSON 



along their sides. Axis of shell is oblique, hatchet-shaped, its ventral mar- 

 gin deeply impressed. Color beneath the periostracum is pink or rose-red. 



M. capax 



II. Periostracum smooth or if provided with bristles, these are more 

 sparingly developed; the individual bristles simple, flattened but not 

 serrated along their sides. Axis of shell not so strongly inclined. 



a. Dorsal and ventral margins are nearly straight and parallel, the pos- 

 terior end attenuated and narrowly rounded. Color on the posterior 

 slope is a reddish purple, the anterior-ventral slope white. 



M. eiseni 



b. Shell obliquely ovate to subtriangular, the anterior side short and 

 quite high, rounded. Color brown with a lighter ray across the middle. 

 Periostracum thin, like patches of flattened seaweed. 



M. -pseudotuUpus 



c. Shell larger, narrower and more elongated. Color dark-brown or black, 

 the surface beneath white. Periostracum smooth. Anterior end short 

 and narrowly rounded. 



M, pacijicus 



Modiolus capax (Conrad) Plate 14, figures 4, 4a 



Modiola capax Conrad, 1837, Jour. Acad. Nat. Sci. Philadelphia, vol. 7, p. 242 San 

 Diego, California.— Reeve, 1857, Conch. Icon., vol. 10, Modiola, pi. 3, fig. 11. 



Volsella (Volsella) capax (Conrad), Hertlein and Strong, 1946, Zoologica, vol. 31, pt. 

 2, p. 72. 



Modiolus capax Conrad, Soot-Ryen, 1955, Allan Hancock Pacific Expeditions, vol. 20, 

 No. 1, pp. 60-62, pi. 6, fig. 30; text-figs. SO, 53a-b, 54, 55. 



Shell of medium or large size (height 85 mm.), heavy, generally obhque, 

 hatchet-shaped, the height often exceeding the length. Dorsal margin 

 straight, merging smoothly into the posterior margin, the two set at angles 

 of 90 to 120 degrees, the posterior-ventral margin rounded to subtruncated. 

 Anterior-ventral side is usually deeply impressed, more markedly so in 

 southern shells. Fresh specimens have a chestnut-colored periostracum, 

 the posterior portion of which is densely covered with long serrated hairs. 

 Dead shells from which the periostracum has exfoliated, are usually colored 

 a bright rose-red over the posterior surface, white on the impressed ventral 

 side. The resilifer is a wide, deeply excavated pit bordered on the lower 

 side by a strong ridge. 



This is a widely distributed species easily distinguished by its high, 

 arcuate form, and coarsely pilose periostracum overlying a red or pink- 

 colored shell. Dead shells have usually lost most of the periostracum, or 

 it is retained only over the posterior portion. 



Range — California southward to Peru and the Galapagos Islands. 

 Panama: Bucaro; Tobago. Canal Zone: Venado Beach. Ecuador: Sua; 

 Manta; Manglaralto; Isla la Plata; Santa Elena. Peru: Tumbez; Paita; 

 Yasila; Sechura Bay. 



Modlolns eiseni Strong and Hertlein Plate 14, figures 5. 5a 



Modiolus eiseni Strong and Hertlein, 1937, Proc. California Acad. Sci., ser. 4, vol. 22, 

 p. 160, pi. 34, figs. 11, 14-16 off Mazatlan, Mexico.— Hertlein and Strong, 1955, 



