VI THE NAUTILUS. 



Somatogyrus amnicoloides Walker, n. sp. (Fig. 3) . 39, 52 



Somatogyrus, apical characters in . . .37, 49 



Somatogyrus crassilabris Walker, n. sp. (Fig. 4) 40, 53 

 Somatogyrus wheeleri Walker, n. sp. (Figs. 1, 2) . . 51 



Sonorella lioderma Pils. (PI. II, f. 7) . . ' 16, 98 



Sonorella lohrii Gabb (PI. II, f. 8) . . 16, 98 



Sonorella merrilli Bartsch . .100 



Sonorella peninsularis Pils. (PI. II, f. 4) 16, 100 



Sonorella ultima Pils. (PI. II, f. 5) . 16, 101 



South Dakota, Mollusca of . 79, 90 



Stain for Radula3 .... .107 



Tethys (Neaphysia) californica (Cooper) . . 84 



Unio cor Conrad, observations on . 102, 114 



Unio crapulus Lea ... . .114 



Unio lewisii Lea . . .114 



Unio viridis Raf. ... . 57, 74 

 Unionidse, some exceptional cases of breeding among the . 4 



Urocoptis cyclostoma anafensis Henderson . 137 



Uruguay, two new bivalve shells from . .112 



Vallonia costata montana Sterki , 126 



Venezuela shells .... .82 



Vitrea carolinensis Ckll .... .27 



Vitrea cryptomphala Clapp, n. sp. (Fig. 1) 25 



Vitrea indentata Say .... .27 



Viviparus malleatus Reeve in Massachusetts 35 



