THE NAUTILUS. Ill 



Unio pustulatus Lea. Bisteueau. 



Unio pustulosus Lea. Blsteneau, Dorcbeat. 



Unio texasensis Lea. Bisteneau. 



Unio trapezoides Lea. Bisteneau, Dorcheat. 



Unio trigonus Lea. Dorcheat. 



Unio tuberculatus Lea. Dorcheat. 



Unio turgidus Lea. Dorcheat. 



Unio zigzag Lea. Bisteneau. 



Margaritana confragosa Say. Bisteneau. 



Anodonta imbecillis Say. Bisteneau, Dorcheat. 



Anodonta stewartiana Lea. Bisteneau. 



Anodonta tetragona Lea. Dorcheat. 



Sphrerium transversum Say. Bisteneau, Dorcheat. 



Campeloma decisa Say. Bisteneau, Dorcheat. 



Yivipara subpurpurea Say. Bisteneau, Dorcheat. 



Physa heterostropha Say. Bisteneau. 



Planorbis trivolvis Say. Bisteneau. 



Amnicola cincinnatiensis Anthony. Bisteneau. 



(Extract from Proc. Cal. Acad. Sci. 2(1. Ser., Vol. III.) 

 A NEW VOLUTOID SHELL FROM MONTEREY BAY. 



BY J. J. RIVERS. 



Scaphella (Voluta) Arnheimi. 



Shell regularly formed, elongate-ovate; body whorl more than 

 two-thirds as long as the spire ; the spire an inch long, and made up 

 of six whorls, the terminal nucleus being very small, jwinted and 

 oblique, which latter character places this species in the section 

 Scaphella of Dall. 



Ground color obscure yellow, covered by a layer of chalk-like 

 deposit. The body whorl has some coarse longitudinal elevations 

 and depressions, remnants of former lip extensions, and there are 

 two large patches of dark rusty red at a wide interval which do not 

 appear to form an interrupted band. The ajierture is elegantly 

 formed and measures 1-1 inches long by i inch wide. The inner 

 lip is regularly outlined on the columella ; columellar plaits four, 



