MAZATLAN BIVALVES 117 
Famity UNIONID£. 
Genus ANODONTA, Cuv. 
Anodonta, Cuv. Tabl. Hlém.1798.—Anodon, Oken, 1815. 
166. ANoponTA ciIconta, Gould. 
Anodon ciconia, Gould Proce. Bost. Soc. Nat. Hist. vol. iv. 
p. 92, Nov. 1851 :—Mex. & Cal. Shells, p. 29. 
Anodon sinuata, Swains. (as @ Lam. non A. sinuosa, Ax. s. 
Vert. vol. vi., p. 569, no. 14.) Hot. Conch. p. 29, pl. 16, edit. 
Hani. 
Distinguished from A. anserina, (Brazil,) according to Gould, 
by being thicker, more tumid on the posterior half, epidermis 
and nacre differently coloured. The nearest N. American 
species is A. implicata. It varies in shape, but may generally 
be known by its somewhat solid growth, ventral gape, and 
salmon colour within. In the young shell, the tint is silvery, 
light or flesh colour. ong. 2°32, lat. 4°24, alt. 1°46. 
Hah.—? Mexico, Lieut. Green —Mazatlan; not uncommon ; 
LP’pool & Havre Coll. 
Tablet 523 contains 3 sp. elongated form.—524, 2 sp. inter- 
mediate.—525, 2 sp. produced ventrally, epidermis glossy with 
faint radiating lines of colour.—526, 1 sp. with concentric 
strie near the umbos.—527, 2 sp. distorted. 
Famity MYTILIDA. 
Dr. Dunker is at the present time engaged on a monograph 
of this family, of which the first part only (Monograph of the 
genera Septifer and Dreissena) is as yet published. He has 
however most kindly identified the Mazatlan species with 
his own, and given me much valuable information concerning 
them. The young shells not only of different species, but 
even of different genera, very closely approximate each other. 
The measurements in this family are taken as follows ; long. 
from umbo to posterior extremity ; lat. from dorsal extremity 
of ligament straight across to ventral margin; alt. thickness 
of closed valves. 
