24G PROCEEDINGS OF THE ACADEMY OF [1879. 



several species, which, while agreeing with one group in most of 

 the characters, persistently differ from it in some one feature, and 

 perhaps in this feature the}' agree with the other group. The 

 question then arises, what is to be done in cases where there are 

 aberrant forms, departing from one type in the direction of another, 

 and blending the characters of the two? Are we to say that our 

 groupings are worthless, and the two must be thrown into one? 

 This produces confusion, and stands in the way of systematic 

 study; and besides we will then probably be no nearer the truth, 

 for we shall doubtless find a similar relation between the group 

 thus formed and some other, which will demand a similar consoli- 

 dation. On the other hand, shall we stand by the distinctions we 

 have discovered, and range our transitional or aberrant forms into 

 subgroups by themselves, and designate them by proper appella- 

 tions? We are clearly of the opinion that the latter, judiciously 

 pursued, is the true course, both with regard to convenience of 

 study, and to facilitate the discovery of a natural classification. 

 Without entering into any discussion of the value of these or any 

 other groups as expressions of actual divisions in nature, we pro- 

 pose to adopt this method of ti^eattnent, and to recognize sub- 

 genera or subgroups of whatever dignity, as the facts may seem 

 to warrant. In so doing we find it decidedly preferable to give 

 each group a name by itself, and consider it as standing alone in 

 its proper rank, and not to name it parenthetically as a mere 

 adjunct to the parent group. If we err on the side of too narrow 

 distinctions, this will only lead to renewed researches and ulti- 

 mately to the truth. 



By adopting this course we are also enabled to retain many 

 generic names founded upon good characters as revealed to the 

 authors by the material at their command, and thus give to many 

 investigators deserved credit for work which would otherwise have 

 to be wholly ignored. 



We have in some cases found it necessary to revise and recon- 

 struct the genus in order to bring, if possible, some order out of 

 the confusion into which its literature had fallen. In doing this 

 we have endeavored to give effect to the evident intention of the 

 founder of the genus, and to improve the diagnosis by the aid of 

 more extensive material than he had access to, as well as by the 

 aid of the labors of other investigators. 



It will be well in this connection to point out the structural dis- 



