NO. 1704. A COLLECTION OF SHELLS FROM PERU— BALL. 151 



MYTILUS CHORUS Molina. 



Plate 25, fig. 1. 



Mytilus chorus Molina, Hist, de Chile, 1782, p. 202, ed. 1787, p. 177; Conchologia 

 Iconica, Mytilus, pi. 2, fig. 4. 

 Choro. From Windy Bay, in the southeast part of Independencia Bay. 



Distribution. — From Coqiiimbo, Chile, northward to Peru. Known 

 in Chile as Almeja, or Choro de Concepcion, after Conception Bay, 

 where it abounds. 



Shell large, ovate oblong, bluish with a thick black periostracuni, 

 smooth or concentrically subrugose; anterior end pointed, recurved; 

 distal end rounded, produced; a single denticle at the hinge; the 

 interior white with a bluish margin; byssus strong. 



This is the largest of the mussels on the coast, and is regarded as 

 the best of the edible shellfish. It is collected for the market where 

 plentiful and transported to the principal towns as a standard 

 article of sea food. 



MYTILUS MAGELLANICUS Lamarck. 



Plate 25, fig. 4. 



Mytilus magellanicus Lamarck, Anim. s. Vert., vol. 6, pt. 1, 1819, p. 119; Ency- 

 clop. Meth., pi. 217, fig. 2. 

 Choro. Ancon and Callao Bays. 



Distribution. — From Magellan Straits northward to Chile and 

 Peru; the northern specimens smaller and less rugose than the more 

 southern variety. 



Shell of moderate size, straight, ovate-elongate, ventricose, ante- 

 riorly attenuated, subpyriform, blackish broA\Ti, varying to chestnut, 

 with a thick periostracuni; inside with a bluish nacre somewhat dis- 

 tributed in zones; the exterior feebly concentrically sculptured, the 

 anterior half of the shell w^tli more or less distinct radiating grooves 

 and ridges. 



Distinguishable from the young of M. chorus by the anterior radial 

 sculpture. 



MYTILUS ATER Molina. 



Mylilus (Iter Molina, Hist, de Chile, 1782, p. 203. 



Mytilus orbignyanus Hupe, in Gay, Hist, de Chile, vol. 8, 1854, p. 211, pi. 5, fig. 5. 

 Choro. From rocks along the shore on the northeast side of San Lorenzo Island, 

 Callao Bay. Also taken from the bottom of a small vessel "after a voyage from Callao 

 to the island Lobos de Afuera. 



Distribution. — From Talcahuano, Chile, northward to Ecuador and 

 the Galapagos Islands. 



This species differs from the preceding in being quite smooth, 

 without radiating sculpture, and when full grown does not exceed 

 3 inches in length. It takes the place of Mytilus edulis in the northern 



