136 CALIFORNIA ACADEMY OF SCIENCES. 



logical growth, putting it in a different section with a 

 jaw-breaking name ! It is a parallel to the occurrence of 

 the lamina or "fulcrum" in some helicoid shells, devel- 

 oped from some unusual condition of the animal, but not 

 constant. It is true that such characters may prove use- 

 ful, and therefore in time develop into generic characters, 

 but in cases like this I can onl}- believe them to be path- 

 ological. 



I have examined many specimens of the inscendens form 

 without finding anything to warrant such a division of 

 specimens by an internal and often hidden character, 

 while they appear the same outside. Their variability is 

 quite as great, if not greater, internall}^ than externally, 

 and few such variations are any more reliable as guides 

 to the division into sections, genera, etc. 



Dr. Dall considers the much enlarged figures given in 

 the 3d article as " not characteristic "" — probably because 

 they are somewhat unlike specimens sent to him for the 

 purpose of showing how much variation is to be expected 

 in these shells. I have had figures engraved from photo- 

 graphs showing extreme forms as unlike the original tvpes 

 as can be found. 



BULIMULUS MONTEZUMA Dall. 



From what has been written as to the subspecies of 

 B. vegetiis, it will be evident that this must be considered 

 the mountain form of the group. Numerous living shells 

 were found on the El Taste Mountains. They occurred 

 down to near 1,000 feet elevation, so that their range in- 

 terlocks with that of B . vegetns, between that and 3,000 

 feet, while the intermediate forms were found in this in- 

 terval. Among these are the six which I have called var. 

 vegexs^iza, which unite also some of the characters of 

 section Leptobyrsus, but not equally in all. From their 

 central position thev seem to be nearlv like the original 



