PANAMIC-PACIFIC PELECYPODA 115 



The type locality as given by Gould is the Fiji Islands which is prob- 

 ably incorrect, Valparaiso, Chile, was selected as type locality by Soot-Ryen. 



This species, as here understood, is probably confined largely to the 

 South American coast washed by the Humboldt Current. It is extremely 

 abundant to the south of Lima, at Paracas, and the Bahia de la Inde- 

 pendencia. 



Semlmytilus nonuranus (Pilsbry and Olsson) Plate 17, figure 10 



Modiolus (Modiolus) nonuranus Pilsbry and Olsson, 1935, Nautilus, vol. 49, No. 1, p. 

 16, pi. 1, fig. 3. 



Shell small (generally less than 40 mm.), the small beaks terminal, 

 the short anterior margins hardly passing beyond them. Valves strongly 

 convex, the umbonal slope straight, the ventral margins but little impressed. 

 The periostracum is thin, smoothish, colored brown on the ventral side and 

 a rich black or green-black on the posterior slope, often with a satiny 

 luster. Interior cream-white with a ray of vinaceous of varying intensity 

 under the umbonal slope. 



Length 39.00 mm., height 19.50 mm., diameter 16.50 mm. 



This seems to be a good species, smaller than S. algosus, of a different 

 shape, the posterior side much wider and more rounded, and its range more 

 northerly. It is a common species between Sechura Bay and Lobitos, usually 

 attached to rocks, swept by strong surf waves, which it thickly covers. 



Range — Coast of northwestern Peru. Peru: Nonura Bay and Punta 

 Aguja at the southwestern end of Sechura Bay; Punta Capullana between 

 Talara and Lobitos. 



Genus CHOEOMTTILUS Soot-Ryen, 1952 



Type species by original designation, Mytilus chorus Molina. Coasts 

 of Chile and southern Peru. 



Often large, strongly obliquely ovate-oblong, of a deep blue or purple- 

 black color, the surface smooth and covered by a coarse, black periostracum. 

 Interior white except for the margins which are dark. 



Choromytilus chorus (Molina) Plate 12, figure 10 



Mytilus chorus Molina, 1782, Saggio suUa Storia Naturale del Chile, p. 202.— Reev«, 



1857, Conch. Icon., vol. 10, Mytilus, pi. 2, fig. 4.— Dall, 1909, Proc. U. S. Nat. 



Museum, vol. 37, No. 1704, pp. 151, 257, pi. 25, fig. 1. 

 Choromytilus chorus (Molina), Soot-Ryen, 1955, Allan Hancock Pacific Expeditions, 



vol. 20, No. 1, p. 31, pi. 2, figs. 7, 8; text-fig. 5. 



With general characters of the genus. According to Dall (1909), this 

 is the largest of the mussels along the Chilian and southern Peruvian coast 

 and generally regarded as the best of the edible shell fish. It is known as 

 Choro de Concepcion after Conception Bay in Chile where it abounds. 



Range — Coast of Peru and Chile from Pacasmayo to Tierra del Fuego. 



Choromytilns pallioponctatns (Carpenter) Plate 12, figures 7, 7a 



Mytilus Palliopunctatus Dunker in Carpenter, 1855, Cat. Mazatlan Shells, Brit. Mus., 



p. 118, No. 167 Mazatlan, Mexico. — Reeve, 1857, Conch. Icon., vol. 10, Mytilus, 



pi. 19, fig. 5. 

 Mytilus (Chloromya) palliopunctatus (Dunker), Hertlein and Strong, 1946, Zoologica, 



vol. 31, No. 2, p. 70. 

 Choromytilus palliopunctatus (Carpenter), Soot-Ryen, 1955, Allan Hancock Pacific 



Expeditions, vol. 20, No, 1, pp. 31, 32, pi. 1, fig. 5; text-figs. 4, 13. 



