OLIVA. * 73 



gentle slope midway between high- and low-water mark. Some 

 time after the retreat of the tide, it is found crawling about with 

 much vivacity on the wet sand. The shell, while the animal is 

 moving, is wholly covered with the foot-lobes, and these are 

 entirely concealed with a thick coat of sand. When the first 

 w r ave of the returning tide strikes them, washing off their coat 

 of sand, they instantly bury themselves.* 



0. VOLUTELLA, Lam. PI. It, figs. 49-51. 



Yellowish, bluish gray, chestnut- or chocolate-colored ; the 

 spire and fasciole often }^ellowish and the body-whorl darker- 

 colored ; the latter sometimes faintly marked with longitudinal 

 zigzag strigations ; interior of aperture yellowish to chocolate- 



brown. Length, '15-1 '25 inches. 



Panama to Gulf of California. 



0. rasamola, Duclos (fig. 51), and 0. selasia, Duclos, are syn- 

 onyms ; the latter founded on a water-worn specimen. 



(Jenus OLIVA. (Typical.} 



The Olives form a very distinct group of mollusks, partaking 

 in the form, and porcellanous coating of their shells, in the 

 character of Cypraea on one side and the Volutes on the other 

 side. Like most shells enveloped in the voluminous foot of the 

 animal, the Oliva has no epidermis, and to the same circumstance 

 is to be attributed the want of an operculum. The shell has an 

 under layer with different pattern of coloring, but this is never 

 exposed, unless in worn specimens, or else artificially by the aid 

 of acids ; hence it is evident that, unlike the Cyprsea, which 

 changes its pattern upon becoming mature, the two layers in 

 Oliva are simultaneously produced at all stages of its growth. 



The Olives are tropical in distribution, the species usually 

 being somewhat restricted in geographical area. They live on 

 sandy flats, burrowing under the surface as the tide retires ; 

 they are very active, moving with considerable quickness. 



Many of the species are immediately recognized by peculiar, 

 unvarying patterns of coloring ; others, again, vary so greatly 

 in this respect that it is almost impossible to define them satis- 

 factorily. 



* Adams, Ann. N. Y. Lye., 281, 1852. 

 10 



