1.916,] NATURAL SCIENCES OF PHILADELPHIA. 319 



question by additional field work, and that is rendered more difficult 

 by the vagueness of his locality data. Sometimes we arc aided by a 

 careful reading of all the text of his descriptions. Thus, in reading 

 the descriptions of his 0. subcarinata, bicolor and lacteal one without 

 access to his material might well suppose that he was describing 

 really distinct subspecies from separate colonies in the same region, 

 but to his description of lactea he added a note to the effect that 

 "the above varieties represent a colony of the largest specimens of 

 the strigosa group," etc. From an examination of some of Hemp- 

 hill's material one of the present authors decided that they were not 

 separable before lie noticed that note, and Hemphill was certainly 

 not consistent in sorting these "varieties" for distribution. One 

 might be pardoned, then, for suspecting that his jugalis and intersum, 

 both from the "banks of the Salmon River," represent a similar 

 instance, but an examination of a small amount of material under 

 those names in Clapp's Hemphill collection indicates that they may 

 be distinct and from different colonies. 



In dealing with land snails of the semi-arid region, with their limited 

 locomotive powers and prohibitive environmental barriers between 

 colonies, a colony may be the equivalent of a geographic race or 

 subspecies in other classes of animals. The fact that we do not 

 perceive environmental differences in different colonies which would 

 result in geographic races, may merely represent our ignorance of 

 certain factors or of their importance in snail life. Some perfectly 

 good species and subspecies are known from only one locality. It 

 follows, then, from the foregoing remarks, that if nearly all of the 

 members of a colony or group of colonies vary in the same direction 

 and approximately to the same degree from other colonies occupied 

 by the nearest known relatives, but sporadic individuals of the one 

 are found with the other, then one may perhaps be justified in 

 considering them different subspecies. When not fully satisfied 

 that the difference is of a kind or sufficient in degree to be entitled 

 to specific or subspecific rank, the varietal name may be preceded 

 by the word "form," to distinguish it from a subspecies. There are 

 certain characters which are of doubtful value at all times as sub- 

 specific characters, unless accompanied by other differences. Such, 

 for example, is size, which may be greatly influenced in one or more 

 colonies or portions of colonies by exceptionally favorable or unfavor- 

 able conditions, as where examples from the midst of a dense thicket 



Nautilus, III, 133-134. 



