1896.] NATURAL SCIENCES OF PHILADELPHIA, 407 



oration with rather conspicuous peripheral color bands (forming a 

 ■combination not unlike the reddish streaked lavas and hence, possi- 

 bly protective) ; and lastly 3. To a rugose, peculiar crenulation or 

 wrinkling of the surface of those species not characteristically 

 .smooth. This last character which, for reasons which will presently 

 be shown, is correlated with aridity or alkalinity of environment, 

 may be regarded as having been impressed upon species which first 

 gained a foothold in the arid region and as having persisted to some 

 -extent in their descendants when the latter succeeded in reaching 

 the upper and more congenial zones of the islands. It is character- 

 istically developed in the following species: Bulimulus Darivini, 

 nesioticus and Wolji, Bvlimulxis sculpturatus, Bulimulus rugiferus, 

 partially in Bulimulus Simrothi, and traces of it are perceptible in 

 some specimens of Bulimulus Bauri. The external appearance is 

 such as to suggest that the shell when soft, had been pecked at with 

 a pointed object, leaving small irregular depressions scattered more 

 or less closely over the surface. It never appears in the nuclear 

 whorls, rarely in the earlier ones following the nucleus, and, when 

 a sufficient number of specimens is examined, some will be found 

 in each species which do not exhibit it. The latter often look very 

 unlike the commoner form of the species, and, by those unacquainted 

 with the relation between them and unsupplied with a sufficiently 

 large series for study, might easily be regarded as specifically dis- 

 tinct. 



The wrinkling or indenting of the surface is distinct from the 

 longitudinal turgid plications, or narrow warty prominences seen in 

 Bulimulus mix var. incrassaius, Bulimulus rugulosus and B. ylano' 

 spira; nor is it the same as the granular sculpture found in the two 

 last mentioned species, in some specimens of Bulimulus jacobi and 

 in cinereus, B. Simrothi, rugiferus, and numerous Lower Californian 

 and Peruvian arid region species, such as B. proteus and B. monte- 

 zuma. This sculpture is more ancient in the history of the group, 

 its elements may often be detected on the nuclear whorls and their 

 subsequent development on later turns is often correlated with the 

 presence of epidermal cirrhi or hairs, sometimes numerous enough 

 to form veritable fringes. Something of this is visible in a perfectly 

 preserved young B. Simrothi; in the full grown shell the delicate 

 hairs have fallen or been lost through abrasion. Nevertheless, the 

 extra development of this and the above mentioned plicate sculpture 

 are generally associated in arid regions with the dryness, and in moist 



