504 MAZATLAN UNIVALVES 
interstitiis concavis ; lirulis spiralibus prominentibus, costis 
superantibus ; canali aperture longitudine subequante. 
Only one dead specimen was found of this pretty little 
species, which somewhat resembles in extreme miniature the 
F. Dupetit-Thouarsii, quoted from the Galapagos, Cuming, and, 
(though on the authority of Kiener only,) from Mazatlan. 
Long. °16, long. spir. ‘08, lat. *07, div. 40°. 
Hab.—Mazatlan ; 1 sp. off Chama; LZ’pool Col. 
Tablet 2413 contains the specimen. 
641. Fusts APERTUS 1. s. 
F. t. subelongatd, albida, rufo-fusco irregulariter fasciaté ; 
anfr. nucleosis i. tumentibus, irregularibus ; normalibus iu. 
+... haud valde tumentibus, suturé impressé ; costis radiantibus 
circiter xii. rotundatis, haud valde prominentibus, basin versus 
obhsoletis ; interstitiis parvis ; lirulis spiralibus, costis superan- 
tibus; canali aperto, parum vrecurvato, longitudine aperture 
curtiore. 
The six specimens found of this species were either young 
or fragmentary ; the size of the nucleus betokening a much 
larger shell. It differs from F’. tumens in the spire being less 
elevated, the whirls and ribs (which are more numerous) less 
swollen, and the canal shorter and open. A verfect young sp., 
with 5 whirls, measures long. ‘1, long. spir. *O47, lat. *055, 
div. 40°. . 
Hab.—Mazatlan ; extremely rare, off Spondylus and Chama: 
L’pool Col. 
Tablet 2414 contains 2 young sp. and a fragment of one older. 
642. > Fusus —————, sp. ind. (a.) 
Tablet 2415 contains a minute shell, with 2 large irregular 
nuclear whirls, and a normal whirl, finely canceliated, white, 
of a subconoid shape. 
Hab.—Mazatlan ; 1 sp. off Spondylus; Z’pool Col. 
643. PFustvs —, sp. ind. (b.) 
Tablet 2416 contains a minute transparent shell of 3 whirls, 
of which the first two are swollen and irregular, the third sub- 
