390 MAZATLAN UNIVALVES 
p. 181, but Hinds points out differences, Thes. Conch. p. 184. 
Long. *5, long. spir. °32, lat. ‘16, div. 30°. 
Hab.—Acapuleco, Sonsonati; Mus. Cuming.—Xipixapi, Cum- 
ing.—Mazatlan ; extemely rare; L’pool Col. 
Tablet 1878 contains 1 specimen, presented by R. D. Darbi- 
shire, Esq. 
Hamity PLEUROTOMID 2. 
All the young Pleurotomide examined have the apex normal, 
with about three whirls smooth and subtransparent. The 
opercula in this Suborder, as in Proboscidifera, are very fre- 
quently repaired after fracture.* Whatever be their normal 
condition, they always reconstruct from a central nucleus: a 
circumstance which seems to shew that the variations in oper- 
cula are not of so much importance as in the shells ; the latter 
being almost always repaired after the normal pattern. 
Genus PLEUROTOMA, Lam. 
Journ. Hist. Nat. 1799, pars: canal elongated, operculum 
subtriangular, nucleus at the anterior extremity. 
Turris, (Humph.) Gray, Proc. Zool. Soc. 1847, p. 134. — 
Hf. & Ad. Gen. vol. i. p. 87. (Non Montf.) 
457. PLEUROTOMA FUNICULATA, Val. 
Kien. Icon. Conch. p. 24, no. 18, pl. 16, f. 1.—Rve. Conch. Ie. 
ple hy sp. 95. 
=P. olivacea, var. Rve. loc. cit. (a prim. man.) pl. 4, sp. 27; 
non Sow. Proc. Zool. Soc. 1833, p. 136. 
Surcula (Turris) funiculata, H. g& A. Ad. Gen. i. 88. 
The aspect of the Mazatlan shells is intermediate between 
the figures of Aven. and Rve. They differ from the figure of 
P. olivacea in the widely excavated space of the posterior sinus, 
and in the keeling of the whirls below it. The epidermis in 
the young shells is ashy, in the adult of arich glossy olive. 
There are numerous coarse spiral striz, two of which appear 
above the suture. There are about 10 nearly obsolete coste, 
rising into tubercles at the periphery. Nuclear whirls smooth. 
*'V. Gray on Reproduction of Opercula, Ann. Nat. Hist. 1854, p. 419. 
