70 THE NAUTILUS. 



fornian coast, one a true Mytilus, the other a Septifer. As long ago 

 as 1882, Dr. R. E. C. Stearns* noticed this fact. It would seem, 

 therefore, that the shell called Mytilus bifurcatus by West Coast 

 conchologists requires another name. I have not seen Mytilus mul- 

 tiformis Carpenter, 5 but from the description and measurements of 

 that species I would consider it a distinct polymorphic species or a 

 composite of two species. In the latter case the smooth form may 

 retain Carpenter's name. At all events, nothing like the variability 

 in sculpture or degree of inflation, which Carpenter says character- 

 ize his species, are found in the California!) Mytilus under consider- 

 ation, which is invariably corrugated and never green in color. I 

 would, therefore, in conjunction, with Mr. Raymond, propose that 

 our form " be called Mytilus Stearnsi, since Dr. Stearns was the 

 first to definitely show that a true Mytilus of this type is found on 

 our coast." " Usually the two species can be separated by external 

 characters. In the Mytilus the umbonal (diagonal) ridge is strongly 

 developed, the valves of the adult shell are very deep, and the ven- 

 tral margin is generally incurved. Inside, besides the absence of 

 the septum, there are several denticles at the angle of the hinge 

 line, which are rather stronger than the corresponding crenulations 

 of Septifer bifurcatus; Mytilus is also lighter colored ventrally. 



" I have no doubt Nuttall's shells came from this State, for 

 from Santa Barbara southward it is an extremely abundant species, 

 covering the rocks in places. The Mytilus is smaller and might 

 easily be passed over as the young of Septifer. I have many Septi- 

 fers from Santa Barbara, but no Mytilus among them. I have Sep- 

 tifers from San Diego collected by Crawford, and among these I 

 found the few Mytilus mentioned by Mrs. Williamson." Septifer 

 bifurcatus was collected by Henry Hernphillat San Hippolite Point, 

 Lower California, and Mytilus Stearnsi he found at the same local- 

 ity and also at San Ignacio Lagoon on the peninsula. 



The type of Mytilus Stearnsi Pils. & Raym. (plate 4, figs. 1, 2, 

 3), is a San Diego specimen. So far as the series before me shows, 

 M. Stearnsi does not grow so large as S. bifurcatus, a length of 25' 

 ram., or one inch being a good size, while bifurcatus may measure 

 nearly double that. An " unusually large " specimen of Carpenter's 



*Proc. Acad. Nat. Sci. Phila., 1882, p. 241. See also Dall and Orcutt, 

 Proc. U. S. Nat. Mus., 1885, p. 551, and Keep, West Coast Shells, pp. 171, 

 173. In the latter work Conrad's name is misapplied. 



5 Ma/atlan Catalogue, p. 118. 



