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, cariiia? 5 on the upper part of the last whorl, 

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

 externally. Length, 1*25 mill. 



N. of Culebra IsL, West Indies; 390 fms. 



K. MORCHII, Collin. PL 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 spirally 

 striate ; aperture nearly orbicular, peristome thin and sharp. 



Length, 2'6 mill. 



Maine, northwards. 



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

 Stimpson. 

 R. AEDONIS, Watson. PL 64, fig. 91. 



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

 convex, spirally lirate, 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 i, 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 Prince Edward Is. ; 140 fms. 

 R. PACHIA, Watson. PL 64, fig. 98. 



Scarcely perforate, subtransparent, suture scarcely impressed, 

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

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

 external varix. Length, 2*5 mill. 



Off Pernambuvo, Brazil; 350 fms. 



