528 MAZATLAN UNIVALVES 
varices, which continue over the suture, leaving deep pits, 
and spirally ascending the spire as in Scalaria hexagona. 
Long. 1°34, long. spir. °6, lat. 67, div. 40°. 
Hah—Acapulco, Humboldt & Bonpland.—Mazatlan ; 1 dead 
sp.; L’pool Col. 
Tablet 2510 contains the specimen. 
675. Murex — 
, sp. ind. 
Tablet 2511 contains one extremely young shell with sharp 
ribs, sparsely decussated, white ; and an older one, rubbed, 
which perhaps is not conspecific; bearing a general resem- 
blance to the young of M. erinaceus. 
Hab.—Mazatlan; extremely rare, off Spondylus ; L’pool Col. 
676. MuRICIDEA PAUXILLUS, A. Ad. 
Murex pauxillus, A. Ad. in Proc. Zool. Soe. 1853, p. 71. 
This very small species is known from the young of its con- 
geners by its very elongated form, and its delicate texture and 
sculpture. Between the varices it is transparent, of a light 
horn colour, with spiral purplish brown bands. It has 7 indis- 
tinct varices, not continuous, sharp, crossed by a few spiral 
ribs, of which one, generally bifid, is conspicuous on the spire. 
The whole surface is covered with imbricated layers of growth. 
Labrum with 5 tubercles inside ; labium smooth, not promin- 
ent. Canal rather open, short. Nuclear whirls often solid. 
Operculum Pisanoid, narrow, apex terminal, reddish brown, 
transparent at the edge; scar with a few lines of growth. 
Epidermis extremely thin. An unusually large specimen 
measures long. °55, long. spir. °28, lat, ‘29, div. 33°. 
Hab.—Mazatlan ; rare; L’pool Col. 
Tablet 2512 contains 1 sp. normal state.—2513, 3 do. elong- 
ated, one with operculum in situ, and a separate operculum.— 
2514, 1 sp. spire depressed. 
Tablet 2515 contains 4 (out of 18) opercula which were found 
among the fragments of Spondylus, and which have not been 
identified with any species. They are ovate, with the nucleus 
terminal and rounded ; very thin, orange horn-coloured ; with 
a few ridges of growth and a large muscular scar. 
