78 MAZATLAN BIVALVES 
possibly a distinct species, and closely resembles the W. Indian 
T. granulata. The largest measures long. 1‘5, Jat. 1°66, 
alt. 1°06. 
Hab—W. Coast Mexico, Say.—S. W. Mexico, P. P. C.— 
Mazatlan, 3 specimens with T. histrionica, Z’yool Col.— 
(T. discors) St. Elena and Guacomayo, in sandy mud, 6-9 fm., 
Cuming.—Ecuador, St. Elena, D’ Orbigny.—Panama, Jewett, 
(Gould ms.)—? Do.: common, C. B. Adams. — Guaymas, 
Ineut. Green, (Gould ms.).—(T. tricolor) Puerto Portrero, in 
sandy mud, 11-13 fm. Cuming. 
Tablet 370 contains the small specimen ; and 371, the largest. 
111. TAPES SQUAMOSA, 2. S. 
T. t. parva, subquadratd, oblonga, alba fusco maculata ; 
margine dorsali subrecto, postice angulato ; costis fortibus ab 
umbone prominente radiantibus, liris eoncentricis parte anteriort 
et ventrali decussatis ; parte posteriori liris obsoletis, costis 
ibt interruptis, squamosis, maxime costéd ligamento 
proximad; dentibus 2-3 cardinalibus divergentibus ; sinu 
pallit subovali ; lunuld impressd. 
Remarkable for the strong radiating ribs, broken up into 
scales posteriorly which are very large on the rib next the 
ligament. On the body of the shell these are decussated with 
moderately distant raised concentric lines. The young shell 
has in one valve a long posterior lateral tooth close to the liga- 
ment. This shell measures long. ‘03, lat. 04; the largest valve 
long. ‘09, lat. °115, alt. °05. 
Hab.—Mazatlan; from washings of Chame and Spondyh ; : 
extremely rare; L’pool Col. 
Tablet 372 contains the only 3 valves found. 
Gents ANOMALOCARDIA, Klein. 
Anomalocardia, Schum. 1817, Essai @une Méth. p. 134.—Desh. 
B. M. Cat. Ven. p. 115. 
Triquetra, Blainv. 1818. 
Cytherea, sp. Lam. 
Venus sp. Sow. Phil. &e. 
This small group of Venerida, consisting of species classed 
sometimes with Venus, sometimes with Cytherea, is well char- 
acterized by its irregular growth and extremely small pallial 
sinus. 
