166 PROCEEDIXGfi OF THE XATIOXAL MUSEUM. vol.27. 



OLIVELLA COLUMELLARIS Sowerby. 



OHva columellaris Sowerby, Tankerville Cat., App. 1825, p. xxxiv. — Reeve, 

 Conch. Icon. Olira, 1850, fig. 62. 

 Beach of Sechura Bay, near Matacaballa. 



Distribution. — Central American coast, Panama and southward to 

 Paita and Sechura Bay. 



vShell small, polished, spire acute, short, last whorl expanded in 

 front, feebly axially striated; pale grayish or lead color, with a 

 heavy whitish body callus, and usuall}^ a yellowish spiral band at the 

 middle of the whorl and behind the suture. There is a single strong 

 plait on the anterior edge of the pillar; interior of the aperture pur- 

 ple, showing one paler band. The animal, unlike that of OHva, 

 possesses a small horny operculum. These shells in prehistoric times 

 were used as beads. 



OLIVELLA SEMISTRIATA Gray. 



Olioa semislriata Gray, Zool. Beechey's Voy., 1839, p. 130, pi. 36, fig. 10. 

 Dredged in Sechura Bay, in about 5 fathoms, west of Matacaballa. 



Distribution. — Gulf of California and southward to Sechura Bay. 



This species is very similar to the last, but has a proportionately 

 longer spire and is less compressed in front. Neither of the species 

 has any present economic value. 



MARGINELLA CURTA Sowerby. 



Marginella curta Sowerby, Proc. Zool. Soc. ui London for 1832, p. 105; Thes. 

 Conch., vol. 1, p. 397, pi. 76, figs. 88, 89. 

 Dredged in Sechura Bay, between Bayovar and Matacaballa; found also at the 

 Chincha Islands and Lobos de Afuera Island. 



Distribution. — From Panama southward to Iquique, Cliile. 



Shell small, polished, of a purplish brown, the spire very short, the 

 aperture narrow, nearly as long as the spire, the pillar with four 

 well-marked plaits; the surface without sculpture except faint incre- 

 mental lines. 



This species has no present economic value, but the prehistoric 

 tribes ground off the apex of the spire, strung the shells on a cord, 

 and used them for beads. 



MITRA ORIENTALIS Gray. 



Mitra orientalis Gray, in Griffith's Cuvier, 1834, pi. 40, fig. 5. 

 Taken on rocks of beach at Ancon; one dilapidated specimen. 



Distribution. — ^Valparaiso, north to Ancon. 



Shell elongate, turrited, covered with a thick black periostracum 

 which in drying peels off, coarsely feebly spirall}" striated; the last 

 whorl longer than the spire ; aperture about half as long as the shell, 



