THE NAUTILUS. 105 



They are as follows : Helicorbis Benson, subgenus of Planorbis, to 

 which are referred PL mtidus of Gray's Turton, PI. hemisphserida, 

 and PL umbilicalis Benson ; this group is equivalent to Hippeutis 

 Agassiz, 1837. Trochorbis Benson is based on PL trochoides Ben- 

 son, which is a typical Segmentina, well figured by Hanley and 

 Theobald in the Conchologia Indica, p. 18, pi. xxxix, figs. 4-6, 187G. 

 As Segmentina dates from 1817, it follows that Benson's name is 

 synonymous. Lastly Omalodiscus Benson is proposed ostensibly for 

 the group called by Swainson Spirorbis (1840, not Spirorbis Duudin, 

 Verities, 1800), but the species mentioned under it belong respectively 

 to Tropidiscus Stein, 1850, and Gyraulus Agassiz, 1837. If we re- 

 gard the contents of the group as wrongfully referred to it and take 

 the name merely as a substitution for the preoccupied Spirorbis (of 

 which the type was PL rotunda/us Poiret), it may be applied to a 

 valid section of Planorbis, but if we regard the contents only, the 

 name must be considered a synonym. Under Helicorbis the only 

 species for which a figure is cited is PI. nitidus of Gray's Turton 

 ( = fontanus Lightfoot) which was already the type of Agassiz's 

 Hippeutis, 1837. The others also belong to Hippeutis, but approach 

 more nearly in form to Drepanotrema Crosse and Fischer, 1880. 



While referring to this paper of Benson's it may be mentioned 

 that his genus Laguncula, which is described in it, and has been 

 generally referred to the Assimineidce, but I believe never figured, 

 resembles a very young thin-shelled Lanatia, with a thin horny 

 pauci-spiral operculum recalling that of Chondropoma. On the 

 whole I suspect it more nearly approaches Gremnoconchus than 

 Assiminea, and may eventually be referred to the Litorinidce. It 

 cannot properly be referred to the Viviparida:, where it was placed 

 by H. and A. Adams, and has none of the shell characters of 

 Assiminea. The aperture, while slightly expanded, does not show, 

 in specimens sent from China by Hungerford, anything which may 

 be strictly termed a reflected peristome, and there is no thickened 

 ledge inside the mouth or shelly deposit on the operculum. 



SAMUEL HAKT WRIGHT. 



We regret to announce the death of Dr. Samuel Hart Wright, 

 father of Mr. Berlin H. Wright. Doctor Wright was born Febru 



