No. 1704. A COLLECTION OF SHELLS FROM PERU—DALL. 151 
MYTILUS CHORUS Molina. 
Plate 25, fig. 1. 
Mytilus chorus Moura, Hist. de Chile, 1782, p. 202, ed. 1787, p. 177; Conchologia 
Iconica, Mytilus, pl. 2, fig. 4. 
Choro. From Windy Bay, in the southeast part of Independencia Bay. 
Distribution.—From Coquimbo, 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 periostracum, 
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. Méth., pl. 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 brown, varying to chestnut, 
with a thick periostracum; inside with a bluish nacre somewhat dis- 
tributed in zones; the exterior feebly concentrically sculptured, the 
anterior half of the shell with more or less distinct radiating grooves 
and ridges. 
Distinguishable from the young of M. chorus by the anterior radial 
sculpture. 
MYTILUS ATER Molina. 
Mytilus ater Mona, Hist. de Chile, 1782, p. 203. 
Mytilus orbignyanus Hurk, in Gay, Hist. de Chile, vol. 8, 1854, p. 211, pl. 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 
