MAZATLAN BIVALVES Ly) 
m a position to do so. Hinge teeth, 1 in each valve, rarely 
seen in adult. 
Largest specimen measures long. ‘63, lat. 1°17, alt. °47, 
A broad flat sp. es be AYR SONOS, takes jc 4m 
A long narrow one 5 FAD Eee) eA OGL Waar 2) 
Smallest "3 5 OZ Na petri OAe to ee Oils 
Hab.—According to Forbes, Atlantic Ocean, Boreal Seas, 
Africa, China, Australia.—Canaries, Webb & Berthelot, B. M. 
Cat. Can. Moll. p. 22, no. 195.—New Zealand, Capt. Stokes, 
B. M.—S. solida: Clefts of rocks, 18 fm. St. Elena, Cuming : 
Peru, Lima, Callao, D’ Orbigny, B. M. Cat. p. 58, no. 510.— 
S. distorta, Say, Rhode Is. Jay.—S. Pholadis, Sea of Okotsk, 
Middendorf.—Mazatlan ; in Spondylus Lamarckii, nestling in 
crevices and burrows, also in Chame and Patella Mexicana, 
very rare adult, not common jun.; L’pool & Havre Coll. 
Fossil, Crag, &c. ; very large in the pleistocene beds at Ud- 
devalla, Sweden, R. D. D. 
Tablet 60, 6 young valves.—61, 1 valve and 6 pairs various 
ages and shapes.—62, 1 specimen bored into, and the valves 
cemented open by tube of borer: also 2 fragments to shew 
ligament.—63, A young specimen in hole of Lithodomus cau- 
digerus in Imperator unguis.—64, A specimen in situ in a Ver- 
metus, off back of Spondylus. 
Famity PETRICOLID. 
Genus PETRICOLA, Zam. 
24. PETRICOLA RoBUSTA, Sow. 
Proe. Zool. Soc. 1834, p. 47.—Sow. Thes. Conch. part xv. p. 775, 
no. 14; pl. elxvi. f. 16, 17.—Miiller, Syn. Moll. p. 229, no. 9.— 
Philippi in Zeit. fir Malac. 1848, p. 163, no. 33, quasi sp. 
nov.: edidit Desh. in B. WM. Cat. Veneride, &e. p. 210, no. 10. 
?=P. bulbosa, Gowld’s plates, ms. 
The name of this shell, which was well described by Sow. in 
1834, was appropriated by Philippi in his 37d Century of new 
shells for a supposed new species ; which turns out fortunately 
to bea small specimen of Sow.’s species, and thus confusion of 
synonymy is unexpectedly avoided. Deshayes has unfortu- 
