120 MAZATLAN BIVALVES 
Hab.—Mazatlan ; jun. abundant, rare adult, among sea weeds 
on Chamez, Spondyh, Ostree, Patelle, &c., or in the cavities 
of dead Lithophagi or Balani; L’pool & Havre Coll. 
Tablet 540 contains 5 pairs and 6. pairs of valves, smooth 
form.—541, 7 pairs and 6 pairs of valves, slightly lirate—542, 
11 pairs and 7 pairs of valves, lirate, jun.—543. 7 pairs do. 
adult.—544, 2 pairs and a valve strongly lirate—d545, 2 sp. in 
crevices of Balanus and Lithophagus; another Balanus has a 
crab in situ; off Patella Mexicana.—546, a group in situ 
among Balani, on M. palliopunctatus.—547, 2 sp. one with the 
surface in concentric layers, like Crepidula Lessonii; the 
other with young Nullipore. 
Tablet 548 contains 5 pairs and 4 pairs of valves, greenish 
yar., smooth form.—d49, 7 pairs and 4 pairs of valves, finely 
lirate.—550, 4 pairs and 1 pair of valves, strongly lirate —451, 
1 large valve, fiat and broad. 
Tablet 552 contains 3 pairs and 2 valves, probably belonging 
to this species. 
Genus SEPTIFER, Réel. 
Vide Dunk. Com. Sep. ef Dreis., Marburgh, 1855.—Tichogonia, 
pars, Ressmassler, 1830. 
169. Seprirer Cumineni, Réc/. 
Dunker, Monog. Sept. p. 8, no. 18. 
The few specimens found are too young to identify with 
accuracy. They are covered with fine, granulose ribs, with 
rather long bristly hairs rising up between. The umbonal 
plate is scarcely perceptible in the smallest shells. Hinge line 
erenate, as in M. multiformis. They closely resemble the 
young of S. bilocularis, but geographically agree better with 
the species quoted. The largest specimen measures only -16 
in length. 
Hab—Panama, Mus. Cuming.—Mazatlan; extremely rare, 
jan. on Spondylus ; L’pool Col. 
Tablet 553 contains 3 pairs of different ages. 
Gents MODIOLA, Lam. 
Volsella, Scopeli, 1777 —Modiola, Lam. 1801.— Modiolus, 
Risso, 1826. 
