104 PROCEEDINGS OF THE ACADEMY OF [April, 



ON THE CLASSIFICATION OF SCALPELLIFOEM BARNACLES. 

 BY HENRY A. PILSBRY. 



The genus Scalpellum as at present limited is more numerous in 

 species than any other genus of Cirripedes, comprising about 170. 

 Since nearly all of them live in rather deep water, and only small areas 

 of the sea bottom beyond the 100-fathom hne have been thoroughly 

 explored, we have reason to believe that their number will be vastly 

 augmented by future investigation. 



The species now known are very unequally related. Up to the year 

 1907 not much progress had been made towards a natural classification, 

 although the "key" constructed by Dr. P. P. C. Hoek for the arrange- 

 ment of the Challenger species was a stride in that direction. In 1907 

 two attempts were made to group the species more naturally, and to 

 indicate their phylogenetic relations. Dr. Hoek^ and the present 

 writer^ independently and almost simultaneously proposed to split 

 Scalpellum into a number of subgeneric groups. The two essays were 

 based upon antipodal material, Dr. Hoek's upon East Indian, my own 

 upon American forms. Some divergence in the view taken of the 

 comparative value of characters would be expected ; yet the points of 

 agreement are so numerous that one may entertain the idea of attain- 

 ing an approximately natural arrangement by uniting the best features 

 of the two classifications. 



Hoek's studies have illumined the more primitive groups so richly 

 represented in the East — forms inadequately represented in the col- 

 lections I had studied. On the other hand, the material before me 

 demonstrated, I think, that the form of the carina has Httle value in 

 classification. Groups based upon the structure of this plate I believe 

 to be heterogeneous. I was first led to this conclusion by an exami- 

 nation of the species composing the group of Scalpellum stroemii, as 

 assembled in my report on the barnacles of the National Museum. 

 These forms agree so completely in the total structure that it is quite 

 impossible to doubt their close relationship, yet the carina varies 



1 Siboga-Expeditie, Cirripedia Pedunculata, p. 58. October, 1907. 



2 B^illetin 60, U. S. National Museum, p. 71. November 9, 1907. 



