MAZATLAN UNIVALVES 367 
the whirls more regularly divergent, and not so tumid towards 
the end. This has the same kind of sculpture on the nucleoid 
whirls, but is wanting in the spiral line which is characteristic 
of the Mazatlan shell. An adolescent sp. with three subnormal 
whirls, measures long. ‘067, long. spir.°04, lat. °035, div. 30°. 
The largest PA es ies oy A 2bie es,  GO755!,; eee 
Hab.— Mazatlan ; very rare, on Chama and Spondylus ; 
P’pool Col. 
Tablet 1723 contains a young sp., the most perfect adult, and 
a broken sp. with the nuclear portion distinct. 
426. ALABA VIOLACEA, 2. s. 
A. t. solidiore, conicd, levi; anfr. primis levibus, tumidis, 
violaceis, pavum divergentibus, haud planatis, suturis impressts, 
albidis ; peripheria vie angulatd, wmbilico nullo; superficie 
transversim minutissime rugulosd. 
This shell has unfortunately lost its apical whirl, and the 
last ; but the characters are sufficiently distinct. It differs from 
A. supralirata in the smoothness and tumidity of the tuberose 
_ whirls ; and in the extremely minute corrugation of the other- 
wise smooth surface, in which it agrees with A. mutans and 
?Chrysallida clausiliformis. The specimen has three normal 
whirls ; and measures (allowing for the apex) long. °06, long. 
spir. ‘037, lat. °032, div. 35°. 
Hab.—Mazatlan ; 1 sp. off Spondylus ; L’pool Col. 
Tablet 1724 contains the specimen. 
427. ALABA TEREBRALIS, 2. s. 
A. t. solidd, conicd, apicem versus acutissime terebrante, albo- 
fusca, levi; anfr. primis parun rotundatis, maxime elongatis, 
angustissimis, marginibus pene parallelis; anfr. normalibus 
planatis, suturis haud monstrantibus, marginibus spire dila- 
tantibus ; bast parum rotundata, wmbilico nullo. 
The only specimen found is ina similarly imperfect state 
with that of the last species ; from which it differs in the great 
elongation of the less swollen tuberous whirls, and in the 
Kulima-like aspect of the flattened normal whirls. Of these 
there are four; and the specimen measures long. ‘067, long. 
spir. 045, laut. °03,. div. 40°. 
Hab.—Mazatlan ; 1 sp. off Spondylus ; Z’pool Col. 
Tablet 1725 contains the specimen. 
