NO. 1704. A COLLECTION OF SHELLS FROM PERU— DALE. 173 



pure white; aperture simple, semilunate without denticulation, and 

 the base without umbiUcus. 



These pretty little black and white snails are phytophagous, and 

 too small to be of use for food, yet they form one of the most widely 

 and commonly distributed and characteristic species of the Peruvian 

 province. 



LITTORINA VARIA Sowerby. 



Littorina varia Sowerby, Genera of Shells, fascic. 37, 1832, fig. 3. — Philippi, 

 Abb. und Beschr., vol. 2, Littorina, pi. 1, figs. 2, 3. 

 Near Capon, oyster beds of Matapalo; found crawling high on the branches of the 

 mangroves, where they are extremely common in the mangrove swamps. 



Distribution. — Gulf of California and southward to Peru. 



Shell larger and proportionately thinner than the ])receding species, 

 spirally threaded, of a pale purple, grayish, or brownish color more 

 or less articulated, streaked, or dotted with darker shades. 



This species is large enough to be eaten like the English "peri- 

 winkle," but no data to the effect that it is actually so used have come 

 to hand. 



CRUCIBULUM IMBRICATUM Sowerby. 



Calyptrsea imhricata Sowerby, Gen. Shells, fascic. 23, 1824, Calyptrxa, fig. 5. 

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



Distribution. — Gulf of California, and southward to the Galapagos 

 Islands and Valparaiso, Chile. 



Shell conical, irregularly marginate, according to the object upon 

 which it is seated, of a brownish color, with emphatic radial appressed 

 imbrications and deep interstices, the interior purplish brown or yel- 

 low, with a thin internal cup-like process attached on one side to the 

 dome of the shell. It sometimes reaches a diameter of 70 mm. 



A singular and characteristic limpet, of no economic importance. 



CRUCIBULUM SPINOSUM Sowerby. 



Calyptrsea spinosa Sowerby, Gen. Shells, fascic. 23, 1824, Calyptrsea, figs. 4, 7. 

 From the flats at Capon, and near Matacaballa, Sechura Bay, Peru. 



Distribution. — California, and southward to Valparaiso, Chile, and 

 the Galapagos Islands. 



Shell resembling the preceding species in a general way, but less 

 heavy, lighter in color, and with the upper surface faintly concen- 

 trically striated, and with more or less developed subtubular spines 

 varying in different specimens from mere low tubercles to long ele- 

 vated spines. It reaches only about 30 mm. in diameter, as a rule, 

 and is of no economic importance. 



