A476 MAZATLAN UNIVALVES 
But in some few specimens the labial callosity is no larger 
than in some of P. patula,jun.: the labral teeth are scarcely 
developed: the mouth is more open, and the sculpture less 
decided. It then so closely resembles young specimens of 
P. patula that they can only be separated by a balance of 
characters. The opercula examined scarcely differ from 
those of P. patula except in their lighter colour. There 
were however none of P. patula, jun. of the same size to 
compare with them. The largest normal specimen mea- 
sures long. 1°58, long. spir.°5, lat. 1°14, div. 90°. 
An elevated sp. aA SAD: A Boy Re aay ween TUL 
Thelargest,abnorm.,, 2°12, TOLs gg Le ae OL: 
The smallest adult ,, 97, A 146. oo SST ae Oe- 
Hab.—Galapagos, Cuming—Mazatlan ; not uncommon, often 
rubbed, but rarely encrusted ; L’pool Col. 
Tablet 2221 contains 4 sp. normal.—2222, 1 do. with opercu- 
lum.—2223, 4 sp. elevated spire.—2224, 5 sp. aperture con- 
tracted.—2225, 7 do. aperture deformed.—2226, 2 sp. sculpture 
well developed.—2227, 4: sp. columellar fold evanescent.—2228, 
3 do. closely approaching P. patula. —2229, 3 opercula, of 
which one is abnormal, with subcentral nucleus. 
€ 
605. Purpura mMuricata, Gray. 
Monoceros muricatum, Rve. Conch. Ic. pl. 2, sp. 7. 
Monoceros muricatus, Mke. in Zeit. f. Mal. 1850, p. 179, no. 45. 
=Purpura cassidiformis (Blainv.) D Orb. B. M. Cat. Moll. 
p. 41, no. 361. 
= Purpura truncata, Ducl. teste Mke. 
This shell rests its claim to a place in the genus Monoceros 
on a projecting wave in the labrum between the canal and the 
first costal depression. Of the true Acanthine Purpuride, 
the almost peculiar possession of the West Coast of America, 
not a single specimen occurred. The few Mazatlan specimens 
of this shell are strongly foliated over the principal spiral ribs, 
and almost always encrusted. The operculum is not so small 
in proportion as in P. patula, with the margins well rounded, 
and of areddish chocolate colour. ‘‘Deckel hornig, biegsam, 
durchscheinend,” Mike. Long. 2°52, lang. spir. ‘54, lat. 2°2, 
dzoe tS, 
