1916.] NATURAL SCIENCES OF PHILADELPHIA. 317 



Limestone is common at almost every locality visited, this being 

 a favorable condition for Oreohelix. The edges of coarse, angular 

 limestone talus protected from rapid evaporation by overhanging 



1 tushes, formed the cover for some of the finest colonies we have seen, 

 the snails occupying crevices among the rocks. At other localities 

 they were abundant under vegetation on limestone slopes totally 

 devoid of talus, and in a few instances they were found in talus where 

 no limestone was observed, though it is almost certain that the soil 

 or rock must have contained a fair percentage of lime in such cases. 

 As some forms were discovered at but one or two stations, we could 

 not determine whether each form chooses definitely a particular 

 kind of cover, but the widely-distributed depressa is found 

 indifferently under either rock or vegetative cover. The kind of 

 vegetation did not seem to be important except as affecting its value 

 as a cover to protect the snails from the sun's rays. 



In the lots obtained after the first few days of September very 

 few embryos were found. This is unfortunate, as the sculpture 

 and shape of the embryonic whorls are important in classification 

 and they are often much worn in adults. The summer was hot and 

 extremely dry and snails of course were dormant — over ninety days 

 without measurable rain. After the rains commenced on September 



2 they became active and filled with water, and large numbers were 

 found in copulation. 



A very noticeable feature of the season's catch is the great difference 

 in the color banding of various colonies of what would otherwise be 

 considered the same form. The protean 0. peripherica (Ancey) is a 

 remarkable example, but scarcely less noteworthy than 0. s. depressa 

 (Ckll.) and some others. The important fact is that where the 

 banding is weak or wanting on some specimens and strong on others 

 from the same colony, the faintness or absence of bands is most pro- 

 nounced on the last whorl. This would be interpreted, under the 

 recapitulation theory, to indicate that the color banding is an ancient 

 character of this genus and is in process of disappearing. 



The question of recognizing subspecies, varieties and color forms 

 is an ever-recurring one in this genus, many of whose species vary 

 greatly in color, form and sculpture. The practice in American 

 ornithology and mammalogy is to give subspecific rank to geographic 

 races where the great majority of examples in one area differ in the 

 same direction and degree from those of another area. The presence 

 of a smaller number of intergrading forms within the range of either 

 and especially along the common border prohibits specific rank, 



