316 MAZATLAN UNIVALVES 
slowly enlarging shell; and by the plug, which is nearly flat, 
with a very small knob on the right side of the back. This, 
under a high power, appears to be of a subspiral growth, like 
a tiny Vitrinella fixed on the surface. The operculum appears 
to be thinner than that of C. liratocinctum, with rather more 
numerous whirls and a finer spiral ridge. It is known at once 
from the dextral specimens of that species by the very fine 
ribs being straight, never spiral, and by the apex being round, 
not pointed. 
The youngest specimen measures long. ‘05, lat. °CO7—O1. 
The largest a a 5 DDS O25 03: 
Hah.—Mazatlan ; off Spondylus; extremely rare ; L’pool Col. 
Tablet 1515 contains 2 very young specimens, the largest 
adult, and a fragment retaining its operculum. 
362. CHCUM ABNORMALE, 7%. S. 
CO. (Elephantulum) t. (?abnormaliter) curtissimd, arcuaté, 
latiore, tenuiore ; lirulis tenvissimis circiter xxx. ornatd, aper- 
turam varicosam tumentem supereuntibus ; interstitiis interdum 
minutissime concentricé striatis ; septo mucronate, prominente ; 
mucrone omnino dextrorsum lateraliter sito, obtusiore ; margine 
laterali (i. e. hoc specie, dorsali) coneavo, rapidé ascendente ; 
operculo ?.... 
Whether this be an extremely short deformed variety of 
C. subspirale, or a very aberrant species, cannot be affirmed 
until more specimens are found. It is common among Ceea, 
in the process of growth, for specimens of the same age to vary 
greatly in length; but these shells, as shewn by the stout 
varix at the mouth, are mature; and yet, contrary to the habit 
of Elephantulum, they are much shorter in proportion even 
than in the compact group Inflatulum. They are so much 
bent that. notwithstanding their shortness, both the surface of 
the plug and the interior of the mouth can be inspected with- 
out.altering the position of the shell. Another very singular 
feature is the position of the plug, which is set on the extreme 
right, so that the front (or back) view of the shell gives its 
profile. One specimen measures Jong. ‘06, lat, ‘023; the other, 
long. ‘048, lat. °018. 
Hab.—Mazatlan ; 2 sp. off Spondylus ; L’pool Col. 
Tablet 1516 contains one specimen. 
