348 RissoiA. 



that species in Gould's Invertebrata of Massachusetts (fig. 75), 

 must represent an extreme variety. 



R. BRACHiA, Watson. PI. 64, fig. 90. 



Umbilicated, thin, translucent, whitish; whorls 4, rounded, 

 spirally carinated, carin;e 5 on the upj^er part of the last whorl, 

 with several less distinct ones on the base ; outer lip sharp, varicose 

 externally. Length, 1*25 mill. 



N'. of Cidebra IsL, West Indies ; 390 fms. 



R. MoRCHii, Collin. PI. 69, fig. 56. 



Narrowly perforate, semipellucid, yellowish brown, apex obtuse ; 

 whorls 4, convex, with channeled suture, spirally ridged, about 

 eight ridges on the last whorl. Length, 3 mill. 



Siberian Sea. 

 R. CARiNATA, Mighels and Adams. PI. 63, fig. 76. 



Shell very thin, ferruginous ; whorls 5, convex, the upper ones 

 with longitudinal ribs, the lower half of the body whorl sjjirally 

 striate ; aperture nearly orbicular, peristome thin and sharp. 



Length, 2*6 mill. 



Maine, northwards. 



It is R. semicostata, Migh. and Ad. (not Mtg.), and B. pelagica, 

 Stimpson. 

 R. AED0NI8, Watson. PI. 64, fig. 91. 



Rather strong, subtransparent, white, apex blunt ; whorls 5, 

 convex, spirally Urate, about 15 on the last whorl, the interspaces 

 much wider; outer lip sharp, thin. Length, 2'5 mill. 



Nightingale IsL, Tristan da Cunha ; 100 to 150 fms. 



R. TRANSENNA, Watson. PL 64, fig. 100. 



Narrowly umbilicated, apex obtuse, translucent white; whorls 

 5-5-2, moderately rounded, with a smooth space below the suture, 

 then spiral threads, 16-18 on the body whorl, separated by wider 

 interspaces ; outer lip sharp, with a feeble external varix. 



Length, 2"5 mill. 



Between Marion and Brinee Edward Is.; 140 fms. 

 R. PACHiA, Watson. PI. 64, fig. 9.S. 



Scarcely perforate, subtrans])arent, suture scarcely impressed, 

 wliite ; whorls 5, narrowly, concavely shouldered, then convex, with 

 faint spiral threads and wider interspaces ; lip sharp, with a remote 

 external varix. Lengtli, 2'5 mill. 



Off Bernambuco, Brazil; 350 fms. 



