MAZATLAN BIVALVES IGL 
Tablet 706 contains a young valve, °68 long, anda larger 
pair, broad spreading form, hinge straight.—707, 1 do. hinge 
spiral.—708, 3 pairs and a valve, different ages, forms and 
colours.—709, Arca grandis, with valves of O. Virginica at- 
tached.—710, an adult sp. attached to a twig, with another 
valve, 4°5 long, attached to it by its whole length.—Another 
of intermediate size will be found on tablet 20; and a vaive 
with Crucibulum. 
Tablet 711 contains a very small Gryphea-shaped shell, 
with spiral umbos, ‘11 in length, which is probably the young 
of this species. 
213. Ostrea CoLumBieEnsis, Hani. 
Proc. Zool. Soc. 1845, p. 107 :—non Ostrea sp. ind. ec, C. B. Ad. 
Pan. Shells, p. 246, no. 382. 
Shell inside without denticles, of a pure white, resembling a 
small O. edulis; hinge area very small. Outside smooth, or 
with lamine of growth ; light ash, with numerous narrow rays 
of purple. Rather thin, flat, attached by the whole surface. 
The largest valve (abnormally produced) measures long. 1°55, 
lat. 1°24. 
Hab.—St. Elena; adhering to rocks at half-tide; Cuming.— 
Mazatlan ; on shells and barnacle-covered rocks, very rare ; 
LT’pool Col.—Lower California, on Arca grandis, Gould’s Col. 
Tablet 712 contains a very young pair, detached, and a valve 
on Imperator unguis.—713, 2 upper valves.—714, 2 pairs, very 
flat and under valve spreading, probably belonging to this 
species, though approaching some forms of O. Virginica, jun. 
214. OsTREA CONCHAPHILA, 2. S. 
O. t. plerumque parva, tenui, subovali, testis variis affixd ; 
purpured, sepe aurantid tinctd, interdum radiis und vel duabus ; 
cardine parvo, utroque latere denticulis crenato ; ared ligamenti 
angusta, triangulari, sepius suleo denticulato utrdque parte 
extus ornata; plerumque totad valoda affixd, margine integro, 
sed interdum subiter ascendente, margine undato, vix plicato ; 
intus subnacreo, cicatrice modico, irregulari. 
?=Ostrea sp. ind. c, C. B. Ad. Pan. Shells, p. 246, no. 382. 
Shell, when delicately grown among Pinne and Anomiz, 
closely resembling QO. bicolor, Hanl. (Proc. Zool. Soc. 1845, 
p. 107 :—Conch. Misc. pl. 1, f.2: supposed to be from West 
