MAZATLAN BIVALVES 155 
Hab.—Bay of Panama, in a few fathoms of water, Cuming ; 
C. B. Adams.— La Paz; Lieut. Green.— Mazatlan; not 
uncommon ; L’pool & Havre Coll. 
Tablet 692 contains a young specimen perhaps belonging 
to this species, but differing from the rest in having the liga- 
mental groove closed, and the scaly processes larger and more 
spathulate : long. 2°3. 
Tablet 693 contains a very young, ,highly coloured valve, 
*22 across. 
Tablet 694 contains a young sp. from Pinna, with Ostree, 
Vermetide, &e. attached: long. 4’. 
Tablet 695 contains a finely grown adult sp., with Verme- 
~ tide, Chama &e. attached. 
Tablet 696 contains a sp. presented by F. Bacon, Esq., 
displaying the interior. The outside contains burrows of 
Parapholas calva, Gastrochena ovata and truncata, Lithopha- 
gus aristatus and plumula, &c. Two Pholads remain in situ, 
having forced themselves against the interior of the shell. 
Tablet 697 contains a fragment of an attached valve, 2°5 in. 
thick, with numerous burrows, displaying the white marble- 
like interior portion, and the coloured exterior bored by 
worms.—698, 2 fragments displaying the colour layers.—699, a 
fragment exhibiting the orange red colour. 
209. ? SeonpYLUs ————-, sp. ind. 
Tablet 700 contains a fragment with very large flattened 
tubercular knobs. 
Hab.—Mazatlan ; in Chama washings ; L’pool Col. 
Genus PLICATULA, Zam. 
210. PLIcaATULA PENICILLATA, %. Ss. 
P. t. alba, brunneo sepe tenue penicillatd, elongatd, haud 
valde costata, margine plerumque plicatd; dentibus cardinali- 
bus elongatis, rugosis, externis magnis valde extantibus ; internis 
angustis, ligamentum ninimum tubulatum amplectentibus ; cica- 
trice musculari subcirculari seu subovali. 
Plicatula dubia, var., Sow. ms. in Mus. Cuming. 
A small specimen in Mr. Cuming’s collection did not present 
sufficiently marked characters, in the judgment of Mr. Sowerby, 
