MAZATLAN UNIVALVES 463 
the Gibberule, Gen. i. 193,) in the absence of parietal lip. A 
slight twist in the upper plaits in some positions gives the 
appearance of an additional fold. The posterior canal and 
callosity are seen in the young shell as well as the adult. The 
smallest sp. measures ‘032 by 021; the largest, long. ‘073, 
lat. *O47. 
Hab.—Mazatlan ; rare, off Chama and Spondylus ; Z’pool Col. 
Tablet 2109 contains 5 sp. young and 2? adult, varying some- 
what in the amount of prominence above the spire. 
Famity OLIVID/. 
There are so few specific marks in the shells of this family, 
and the painting (which is most relied on) is so variable, that — 
the species intended by different authors cannot always be 
recognized. Until large series have been collated from various 
localities, and their animals have been examined, allied forms 
can only be provisionally regist-red. One species, O. porphyria, 
stands alone in its distinctness. It was found in the S. W. 
Mexican collection, and also in a box of shells from the same 
province abounding in Terebra variegata, a very large rough 
Pecten, and other shells not found at Mazatlan. It is indeed 
quoted by Menke, Zeit.,f. Mal. 1851, p. 23, no. 100,) but as his 
list includes bought shells, it is not of undisputed authority ; 
and the entire absence of so large and attractive a species from 
so vast a collection as that here described is negative evidence 
of no little weight. At the same time it is probable that some 
Olive are migratory creatures ; and this may have been absent 
during the period that the industrious Professor Reigen was 
ransacking the ocean bed. 
Genus OLIVA, Brug. 
Encycel, Meth. p. 15, no. 38, 1792, (pars). 
Dactylus (lein) H. § A. Ad. Gen. vol. i. p. 142. 
590. Oniva ANGULATA, Lam. 
Ann. Mus. vol. xvi. 1810, p. 310, no. 6:—An. s. Vert. vol. x. 
p. 607, no.6.—Ene. Méth. pl. 363, f.6.— Ducl. Mon. Oliv. 
pl. 17, £.9, 10:—do. in Chénu, pl. 18, f. 9, 10.— Kust. Conch. 
Cab. pl. 2, f.1,2.—Rve. Elem. Conch. pl. 1, f. 4, pl. D.:— 
