MAZATLAN UNIVALVES 363 
421, JEFFREYSIA TUMENS, 2. 8. 
J. t. tumente, diaphand, levi, tenuissimd, albidd; vertice 
depressa ; anfr. WW. converis, marginibus spire exeurvatis ; 
apertura subovali ; umbilico magno, carinato ; operculo tenuis- 
simo, translucido. 
Differs from the least elevated form of J. bifasciata in its 
very swelling and somewhat irregular whirls, transparent 
white texture, and large angulated umbilicus. The operculum, 
which was found in five out of the thirteen specimens, is per- 
fectly transparent, appearing black from the remains of the 
animal, which seems to have been differently coloured from 
- that of J. bifasciata. Long. *048, long. spir.*026, lat. *038, 
div. 55°. 
Hab.— Mazatlan ; very rare, off Chama and Spondylus ; 
TP’pool Col. 
Tablet 1719 contains 2 sp.; one young and glossy, with the 
operculum so situated as to shew the medial process; the 
other adult. 
422, P JEFFREYSIA —, sp. ind. 
Tablet 1720 contains a horny, transparent shell of three 
whirls, exactly like a small Ampullaria. It may possibly be a 
nucleus, but is much more normally shaped than the many 
such that I have examined from this collection. Another im- 
perfect specimen was found with an additional half whirl. 
Long. *046, long. spir. *009, lat. °044, div. 130°. 
Hab.—Mazatlan ; 2 sp. on Chama; L’pool Col. 
Famity TRUNCATELLID-. 
These shells are ranked with Cyclostomide by Phil. and 
C. B. Ad.; with Littorinide by Woodward; doubtfully with 
Pyramidellide by Forbes; between Dentalium and Pyrami- 
della by Gray, 1847; between Czcum and Pyramidella, do. 
1850; between Lacuna and Planaxis, do. 1855. For an account 
of the animal of the Tr. Montagui, v. Clark Moll. Test. Mar. 
Br. p. 380, according to whom it is an undoubted Littorinid. 
