MAZATLAN BIVALVES 21 
Smallest specimen, long. ‘018, Jat. ‘03, alt. ‘015, 
Largest’ i Lom Shee OR Pipe] a be) 
Hab.—Mazatlan; a small colony were found nestled, and 
greatly incommoding each other, in empty Balani on Murex 
princeps: Havre Col. 
Tablet 73 contains 1 specimen in situ, in Balanus ; 3 others 
of different ages. 
29. RUPELLARIA —, sp. ind. 
Tablet 74 contains a fragment resembling R. foliacea, Desh. 
Mazatlan ; with strong radiating ribs crossed by erect and beau- 
tifully undulated lamine. The sculpture smoothes off at the 
hinge margin. 
Hab.—Mazatlan; from the back of a Spondylus Lamarcki ; 
LP’pool Col. 
Famity CORBULID. 
Genus CORBULA, Brug. 
30. CORBULA BICARINATA, Sow. 
Proc. Zool. Soc. 1833, p. 35.—Miull. Syn. Test. Viv. p. 229.— 
Rve. Conch. Ic. 1844, pl. 3. f. 23 —Hanl. in Woods Suppl. 
Ind. Test. pl. 12, f. 31.—Hanl. Desecr. Cat. p. 46.—B. M. Cat. 
D Orb. Moll. p. 70, no. 619. 
Shell extremely swollen, the valves nearly equal, sometimes 
one a little overlapping the other at the posterior ventral margin. 
Epidermis thin over the body, thick over the margins of the 
valves. Irregularly concentrically striated over the surface, 
very finely between the posterior keels: umbonal portion 
smooth. Within, ligament affixed to the smaller tooth: pos- 
terior muscular scar rounded, on a projecting support; a 
smaller one behind: anterior scar oblong. Pallial line simple. 
In the 3 specimens which alone I have had an opportunity of 
examining, which are quite fresh, I cannot detect any pallial 
sinus. Those who have plenty of Corbule would do well to 
examine their interiors, which are not generally noticed in the 
descriptions. They are either very rare at Mazatlan, or have 
escaped detection, scarcely a dozen specimens having been 
found of all the species. Long. 2°7, lat. °36, alt. °28. 
Hab.—In sandy mud, 7—17 fm., Panama, Real Llejos, Caraccas, 
St. Elena, Cawming.—W est Columbia, Hanley, Jay.—Ecuador, 
