528 MAZATLiJI UNIVALVES 



varices, vrliicli continue over tke suture, leaving deep pits, 

 and spirally ascending tlie spire as in Scalaria hexagona. 

 Long. I'M, long. sjni'. '6, lot. '67, div. 40°. 

 Sah. — Acapulco, Humboldt Sf Bonpland. — Mazatlan ; 1 dead 



sp. ; L'pool Col. 



Tablet 2510 contains the specimen. 



675. jVIubex , sp. ind. 



Tablet 2511 contains one extremely youn? shell ^ith sbarp 

 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. 

 Hah. — Mazatlan; extremely rare, off Spondylus ; L'pool Col. 



676. MUEICIDEA PATTXILLTJS, A. Ad. 



Mures pauxillus, A. Ad. in Proc. Zool. Sac. 1853, p. 71. 



This very small species is known from the young of its con- 

 geners bj^ 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 13) opercnla 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 lai*ge muscular scar. 



