(at) 
U MAZATLAN BIVALVES 
Smallest specimen measures long. ‘04, lat. ‘06, alt. ‘02. 
Largest i 53 ey “ADs "72, "24. 
Tablet 101 contains 3 young valves.—102, the largest (imper- 
fect) specimen.—103, a C. lamellosa, which had established 
itself within the empty remains of a Petr. robusta, which had 
itself gone to dwell inside the skeleton of a deceased relative 
which had originally constructed the burrow.* 
The form coarctata was found by Mr. Hanley in Spondylus 
Lamarckii ; Havre Col. 
43, CUMINGIA TRIGONULARIS, Sow. 
Proc. Zool. Soc. 1833, p. 35.—Rve. Conch. Syst. pl. 49, f. 2.— 
C. B. Ad. Pan. Sheils, p. 288, no. 480. 
Lavignon trigonularis, Gray. B. M. Cat. D’ Orb. Moll. p. 59. 
no. 519. 
Tolerably well distinguished by the great projection of the 
ligamental spoon and hinge teeth. The laterals are very short. 
truncated, and of nearly equal length. Pallial sinus very large. 
Decussating strie well developed. N.B. The muscular scars 
often vary in shape with the distortions of the shell. The 
largest specimen found measures long. ‘Di lat. 62, alt. *32. 
Hab.—St. Elena : among stones in deep water, Cwming.— 
Ecuador; St. Elena, D’ Oréigny.—Panama, very rare, C. B. 
Adams.—Mazatlan : nestling in burrows in Spondylus Lam- 
arckii; very rare; L’pool & Havre Coll. 
Tablet 104 contains 1 perfect and 3 broken specimens, of 
various ages. 
4A, CUMINGIA CALIFORNICA, Conr. 
Journ. Ac. Nat. Se. Phil. 18 =, p. 
Teeth and pallial sinus intermediate between C. lamellosa and 
C. trigonularis. Anterior side generally swollen. The largest 
specimen found measures Jong. °33, lat. °52, alt. °22. 
Hab.—Upper California, Nuttall—Mazatlan; nestling in bur- 
rows in Spondylus Lamarckii, very rare ; L’pool Col. 
Tablet 105 contains 1 young, and 2 adult specimens. 
* So I have, in limestone from Weymouth Bay, Sphznia Binghami nestling in 
the tube of a Gastrochena modiolina which had been formed by soldering 
together portions of a Thracia distorta through which it had burrowed. 
