CLASS PELECYPODA 
71 
Subgenus Adula H. & A. Adams, 1857. 
Botula diegensis Dali, 1911. 
Plate 11, figs. 1, 2. 
The Nautilus, 24:10, 110; U. S. N. M. Bull 112; pi. 1, figs. 1, 3. 
Shell small, zoned with dark blue, the umbones usually white, covered 
with an olivaceous brown periostracum; anterior end very short, rounded, 
with two or three radial grooves externally; umbones moderately promi¬ 
nent; dorsal profile ascending, nearly straight, sub-angulate behind, the 
margin carried with a broad sweep to the base where it meets the posterior 
end of an obscure ridge, radiating from the umbos, in front of which 
the valves are more or less constricted and, on the base, flattened, giving 
a slightly arcuate aspect to the shell; valves with a very slight rather 
anterior gape; interior polished, dark blue, much as in Mytilus ediilis, the 
ligament long, the anterior margin with three or four crenulations cor¬ 
responding to the external radial grooves. Length, 19; height, 6.8; 
diameter, 5.5 mm. (Dali.) 
Type in U. S. N. M. Type locality, San Diego, California. 
Range. San Francisco Bay to Cape San Lucas, Lower California. 
Botula falcata Gould, 1851. 
Plate 21, figs. 8, 9. 
Proc. Boston Soc. Nat. Hist., 4:92. Mexico and California Shells; pi. 6, fig. 5. 
Shell fragile, falcate, sub-cylindrical, with a strongly marked angle 
from the beaks to the base of the posterior extremity; beaks at the anterior 
eighth of the length, strongly involute and leaving a deep depression in 
front of them. The anterior extremity is rounded, dilated, broader than 
high; the posterior end is arcuate and acuminate; against the beaks the 
valves are somewhat compressed; the arcuation is produced chiefly by 
the deflection of the superior margin, which is also rather sharp posteriorly. 
The substance of the shell is somewhat pearly when exposed by erosion, 
and is covered by a thick chestiiut-colored epidermis, conspicuously cor¬ 
rugated at every part, in vertical wrinkles posteriorly, but in a somewhat 
divaricated manner anteriorly. The posterior superior portion gives rise 
to a byssoid fringe. Length, 3; height, yi ; diameter, inch. (Gould.) 
Type in Boston Soc. Nat. Hist.? Type locality, Monterey, California. 
Range. Coos Bay, Oregon, to San Diego, California. 
Botula californiensis Philippi, 1847. 
Plate 27, fig. 5. 
Zeitschr. Mai, p. 113. Conch. Cab. ed. 2 ; pi. 5, fig. 19. 
Shell cylindrical, lithophagus-like, smooth, very thin, somewhat pointed, 
sub-nacreous, white, posterior end sometimes tinged with blue; epidermis 
