122 THE NAUTILUS. 



P. hastatus Sowerby, is a good species of small size and limited 

 distribution in the California region. 



P. hericius Gould is distinct, and distributed from Port Althorp, 

 Alaska to San Diego, Cal. The variety albidus Dall, if not a dis- 

 tinct species, is probably an extreme form of hericius. 



P. islandicus Miiller, extends from the Arctic south in constantly 

 deeper water to the Strait of Fuca. Varieties of this were supposed 

 to be P. rubidus Hinds, by Middendorff, who did not know the true 

 rubidus, and his name for one variety, beringiana, takes precedence 

 of my variety strategus, which is identical. 



P. hindsii Carpenter (rubidus Hinds, not Martyn) has a very 

 wide distribution from Bering Sea to Cape St. Lucas. It is a good 

 species, the typical form of which has the major ribs on the right 

 valve flattish and smooth. In my variety navarchus they are rounded 

 and densely imbricate. The two can be separated in the dark. 



Pecten (Plagioctenium) circularis Sowerby, has had a confused 

 nomenclatorial career. It was first named tumidus by Sowerby in 

 1835, but there is an older tumidus of Turton, 1822. Sowerby then 

 replaced the name by ventricosus under which the species is 

 commonly catalogued. But he had also described in 1835 a P. cir- 

 cularis from Guaymas, Mexico, which as figured appears to be merely 

 a color variety of tumidus. There is a P. circularis of Goldfuss, but 

 it appears to have been published in 1836. The species will then 

 (as indicated by Arnold) take the name circularis. It is closely 

 analogous to the Atlantic P. dislocatus Say, and its variety tequisul. 

 catus bears the same relation to the type that the Atlantic irradians 

 does to dislocatus (= gibbus Lam.) 



Pecten (Patinopecteri) caurinus Gould. This species can at once 

 be distinguished from its analogue P. yessoensis Jay, by the fact that 

 its minor surface sculpture is purely concentric, while that of the 

 Japanese shell is reticulate when in perfect condition. 



P. digitatus Hinds, is probably only a young specimen of P. (Nodi- 

 pecten) subnodosus Sowerby. 



A NEW SONORELLA FROM THE GRAND CANYON, ARIZONA. 

 BY JUNIUS HENDERSON. 



Among some shells recently received from Mr. Ellsworth Bethel, 

 of East Denver High School, were four dead specimens of Sonorella 



