22 CALIFORNIA ACADEMY OF SCIENCES. 



however, be as well to continue to regard the original types 

 of west-coast forms as distinct species, the intermediate 

 links being generally confined to narrow geographical limits. 

 It is a still unsettled biological problem whether different 

 species of these low orders of animals may not originate 

 new species by hybridization, some of the progeny being 

 fertile, and perpetuated by natural selection. Mr. Binney, 

 ("Man. of Amer. Land Shells," pp. 122-3, 1885) con- 

 siders the two as identical, or varieties of one species, bvit 

 thev exhibit such a wide difference in their extreme forms 

 as is not seen in any other known species, and must rank at 

 least as sub-species. 



C. ? hifumata presents a curious instance of possibly pre- 

 servative color-variation, as it commences to appear just 

 south of the Oregon boundary, where a drier climate makes 

 fires more frequent, and from its color is less easily 

 seen by enemies among charred logs and leaves, while 

 its lower, angled form, enables it to crawl under logs 

 or into fissures of rocks, where C. ? fidelis cannot thus 

 protect itself. Thus it exists with the depressed forms, 

 11 and 37, as far east as Solano County. The same 

 may be observed of the angled and hirsute race of C. ? mor- 

 monum, called lullebrandl, found in the Sierra Nevada be- 

 tween lat. 37° and lat, 38^. A black variety of C. ? sequoicola 

 has also been found in the Santa Cruz Mountains, where 

 fires are so frequent and destructive, but no angled form 

 of any kind is yet known in the southern Coast Kange, al- 

 though a fossil of that shape occurs on Santa Barbara 

 Island, which I have referred to the living species A. ? trtjoni, 

 now only found rounded. (See Proc. Cal. Acad. VI., 17, 

 1875.) 



It is not uncommon to find colonies of some of the large 

 Helicoids killed by fire, a slight scorching of the shell being 

 sufficient to kill them. It is thus evident that in the dri(ir 

 localities farthest from the coast where fires are likely to 



