SYNONYMY OF ACHATINELLID^E. 11 



authors, except when occasionally some felicitous grouping 

 by one or another student inspired approving comment. 



It would be quite impossible for an investigator knowing 

 these shells only by small museum series, already assorted, 

 and often imperfectly localized, to arrive at right conclusions. 

 Several factors combine to render the recognition of species 

 and races unusually arduous in Achatinella. The absence 

 of differentiation in structural characters is the chief hard- 

 ship. In any allied series the shape is about the same, and 

 the size is remarkably uniform throughout the genus. There 

 are no such extremes of size as in Partulina. Both shape 

 and size vary so much individually and with locality that they 

 cannot often be depended upon to separate allied species, 

 except in the average. There is very rarely any specific 

 sculptural modification ; and finally, the color and pattern are 

 kalaidoscopic in many races, and a special pattern is often 

 produced orthogenetically in several species. 



Any polychromatic species is likely to produce individuals 

 of strange or unusual patterns, sometimes possibly as new 

 mutations, more often as a result of some unusual combina- 

 tion of color-factors in complex hybrid colonies. Such unique 

 or exceptional individuals may readily enough be referred to 

 their proper species if kept with their associates in life; but- 

 separated from their colonies, and without definite locality, 

 it is sometimes almost or quite impossible to tell what racial 

 stock they belong to. A number of the species described by 

 Dr. Pfeiffer from specimens sent by Mr. Frick were evi- 

 dently such exceptional, or as they say, "freak" shells. 

 Any large collection contains shells which, if isolated and 

 described without locality, could be referred to their proper 

 species only with the greatest difficulty if at all. 



A further source of perplexity is the tendency of some 

 species to form melanistic or albinistic mutations. In the 

 absence of structural characters, such forms, when not ac- 

 companied by their associates, and especially if without exact 

 locality, may be difficult or even impossible to refer to their 

 proper species or race. This is particularly true of the Apex 

 or typical group of Achatinella. 



