MAZATLAN UNIVALVES 463 



the Gibberulae, 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. '047. 



Hob. Mazatlan ; rare, off Chama and Spondylus ; L'pool Col. 

 Tablet 2109 contains 5 sp. young and 2 adult, varying some- 

 what in the amount of prominence above the spire. 



FAMILY OLIVIDyE. 



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 registered. 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. Hal. 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 

 Olivse are migratory creatures ; and this may have been absent 

 during the period that the industrious Professor E/eigen was 

 ransacking the ocean bed. 



GENUS OLIVA, Brug. 



Encycl. Meth. p. 15, no. 38, 1792, (pars). 

 Dactylus (Klein) H. $ A. Ad. Gen. vol. i. p. 142. 



590. OLIVA ANGULATA, Lam. 



Ann. Mus. vol. xvi. 1810, 'p. 310, no. 6 : An. s. Vert. vol. x. 

 p. 607, no. Q.Enc. Meth. pi. 363, f. 6 Duel. Hon. Oliv. 

 pi. 17, f. 9, 10 :do. in Chenu, pi. 18, f. 9, IQ.Kust. Conch. 

 Cab. pi. 2, f. 1, 2. Rve. Mem. Conch, pi. 1, f. 4, pi. D. : 



