MAZATLAN UNIVALVES 369 
This shell closely resembles Chrysallida nodosa in form and 
sculpture ; but although the specimens were broken, there is 
no indication of columellar fold ; what remains also of the apex 
accords better with Alaba than with that genus. The char- 
acter of the mouth comes nearest to A. supralirata. Long. °08, 
long. spir. ‘044, lat. °056, div. 50°. 
Hab.—Mazatlan ; 4 sp. off Spondylus ; L’pool Col. 
Tablet 1728 contains the most characteristic specimen, though 
another retains rather more of the apex. 
431. PALABA MUTANS, nom. prov. 
A. t. ovoided, alba; vertice parvo, declivi ; anfr. 1. sequenti- 
bus tumentibus, levibus; dein anfractu uno minus twmente, 
superficie transversim minutissime rugulosd, interdum -costis 
obsoletis transversis ; dein anfractibus normalibus ii., liris 
validis spiralibus cinctig, (in anfr. penult. x.) interstitiis rugulis 
minutissimis transversim ornatis, costis quoque transversis, pene 
obsoletis, aperturam versus evanidis ; basi rotundatd ; apertura 
ovali, ad basin effusd ; rimulé umbilicali ornata ; peritremati 
continuo ; labro a lirulis indentato, labio tenui ; columellé haud 
plicata. 
The shell, in its disparity of whirls, and in the minute 
transverse rugulation of its surface resembles ? Chrysallida 
clausiliformis ; in its ovoid form, the more typical Chrysallide ; 
from which it differs in the entire absence of columellar plait, 
as an otherwise unfortunate breakage on the spire clearly 
proves. It may be a Rissoid, and resembles in many respects 
P Litiopa saxicola, C. B. Ad. Pan. Shells, p. 183, no. 256, (which 
Dr. Gould assigns to Cingula, not having any columellar trun- 
eation, and on the labrum of which, in Mr. Cuming’s specimens, 
there is no deposit, but a continuous peritreme, with an umbili- 
cal chink.) Long. ‘088, long. spir. °048, lat. ‘046, div. 33°. 
Hab.—Mazatlan ; 1 sp. off Spondylus ; L’pool Col. 
Tablet 1729 contains the specimen. 
432, PALABA LAGUNCULA, om. prov. 
2A. t. elongata, albo-fuscd ; vertice tumentiore, declivi ; anfr. 
iv. primis levibus, subplanatis, suturis canali parva, impressa 
instructis, marginibus spire valde excurvatis ; dein subito liris 
spiralibus validis, rotundatis, extantibus ; interstitiis parvis, 
decussatis; ..... 
