THE NAUTILUS. 69 



seems to vest upon the presence or absence of a septum. As this 

 generic character may he present or absent in some of the shells 

 found in the same place, an interrogation naturally arises as to the 

 value to be placed upon the septum in separating approximate forms 

 into two different subfamilies, the Mytilinre and Dreisseusinre. 



NOTE ON SEPTIFER BIFURCATUS CONRAD. 

 BY H. A. PILSBRY AND W. J. RAYMOND. 1 



Among the shells brought home by Thomas Nuttall from his jour- 

 ney to the Pacific coast and the Hawaiian Islands, were specimens 

 of a mussel which Conrad named Mytilus bifurcatus? Two speci- 

 mens of this species were presented by Nuttull to the Academy of 

 Natural Sciences, 3 where they are still preserved. 



Conrad gave the locality " Sandwich Is." for his species; but the 

 specimens were probably from California. In the Conchologia Icon- 

 ica, vol. 10, Mytilus, pi. 9, fig. 41 (1851), Reeve figures and de- 

 scribes a specimen from Cuming's collection as Mytilus bifurcatus 

 Conrad, giving no locality. I do not know that the interior of this 

 shell has been examined ; but Nuttall's shells in the Academy col- 

 lection prove to belong to the genus Septifer, having a well-developed 

 septum or little deck across the apices of the valve cavities. There 

 is no especial reason for believing Reeve's specimen to be a true 

 Mytilus; but if they should be, the name M. bifurcatus Reeve can- 

 not be retained, on account of the conflict with Conrad's prior M. 

 bifurcatus. 



As Mrs. Williamson's article (above) shows, California!! conchol- 

 ogists find two species excessively similar externally upon the Call- 



1 In placing Mr. Raymond's name with my own, it should be mentioned that 

 he is directly responsible only for the passages placed in quotation marks ; 

 though indirectly for the positions taken in the remainder of the article. H. 

 A. P. 



2 Journal of the Academy of Natural Sciences of Philadelphia, VII, 1834, 

 p. 241, pi. 18, fig. 14. 



3 Neither of these shells seems to be the original of Conrad's figure, and 

 probably that particular shell has been smashed and discarded, the specimens 

 having been glued to a card and consequently exposed to such accidents. A 

 nearly complete series of Nuttall's shells is in the Academy Collection, includ- 

 ing some not described by Conrad. 



