MAZATLAN UNIVALVES 429 
profunde excavatis ; basi levi, rotundatd ; labro tenui ; colu- 
mella eleganter inflexd. 
This beautiful little species closely resembles Ch. turrita, 
C.B Ad. Pan Shells, no. 230, pp. 169, 312; from which it 
differs in the entire absence of spiral keels at the base. The 
apical whirls are extremely tumid; the rest are all flat, com- 
pact, and somewhat muricated at the sutures by the projecting 
ribs. Long. 09, long. spir. 07, lat *027, div. 13°, 
Hab.—Mazatlan ; 5 sp. off Spondylus ; L’pool Col. 
Tablet 1993 contains 2 sp. differing in texture, and in the 
position of the apex, but probably conspecific. 
(b.) Ribs more or less continuous over the base. 
523. CHEMNITzIA PAFFINIS, C. B. Ad. 
Pan. Shells, no. 221, pp. 165, 311. 
Although this species is described as “‘very smooth ante- 
riorly,” the type specimen in Mr. Cuming’s collection is 
distinctly striated spirally round the base, over which there is 
a very faint indication of the ribs: apex scarcely projecting, 
of two whirls. The Mazatlan specimen is rubbed; it has 
seven whirls and measures Jong. ‘068, lat. °03, div. 20°. 
Hah.—Panama; 2 sp.inthe sand; C. B. Adams.—? Mazatlan ; 
1 sp. off Chama; L’pool Col. 
Tablet 1994 contains the specimen. 
524. CHEMNITZIA PROLONGATA, 2. 8. 
s 
Ch. t. elongata, gracili, tereti, albida ; vertice nucleoso anfr. ii. 
helicoideis, marginihus spire subrectis haud superante ; anfr. 
normalibus xi. subconvexis, suturis tmpressis ; costis subacutis 
ceirciter xxil., haud continuis, vie declivibus, ad basin tenue 
prolongatis, ad rinulam umbilicalem ascendentibus ; aper- 
turd ovata; labro acuto ; columella eleganter intorta. 
This graceful species, a little group of which was discovered 
in a cavity on Spondylus by Mr. Darbishire, is aistinguished 
from similar West coast species by the faint prolongation of 
the rather slender ribs over the base to the umbilical chink 
formed by the slight twisting of the columella. The nuclear 
vertex is not broader than the next whirl. An adult specimen 
measures long. °215, long. spir. ‘175, lat. °05, div. 13°. 
