310 MR. E. A. SMITH ON THE [Apr. 1, 



g subcequans ; peristoma tenue, marciine columellari leviter 

 reflexo, superne labro callo tenui juncto. 

 Lonr/it. 2 millim., diani. 1. 



This species has more convex whorls than S. varicifera, to which 

 it bears a general resemblance. Its spiral ridges also are finer, the 

 aperture different, and the labrum has no external varix. 



RissoA siMULANS. (Plate XXIV. fig. 16.) 



Testa ovata, imperforata, alba vel pallich fuscescens ; anfractus 

 4, convexi, primus et secundus spiraliter striati, seqventes liris 

 transversis {in anfr. jJenidtimo circiter 3, in ultimo 8-9) in- 

 structi ; apertura rotunde ovata, lonyit. totius | paulo minor ; 

 peristoma continuum, vix incrassatum, marr/ine columellari 

 anguste rejlexo. 



Longit. 1| millim., diam. 1. 



This is a shorter stumpier species than _B. varicifera and has no 

 postlabral thickening. 



RissoA oRDiNARiA. (Plate XXIV. fig. 17.) 



Testa ovata, soUdiuscula, alba, imperforata, nitida ; anfractus 

 4, convexiuscidi, sutura mediocriter profunda, paulo obliqua 

 sejuncti, spiraliter substriati ; apertura rotunde ovata, superne 

 acuminata, longit. totius g paxdo superans ; peristoma continuum, 

 leviter incrassatum,, margine columellari dilatato. 



Longit. Ig millim., diam. |. 



This species, although so small, is certainly adult. The spiral 

 strise are not numerous, and only visible on well-preserved specimens 

 by the aid of a microscope. 



RissoA ^auA. (Plate XXIV. fig. 18.) 



Testa brevis, turrita, alba, vix rimata ; anfractus 5, primi duo 

 convexi, laves vel spiraliter tenuiter striati, cceteri superne 

 tabulati, angulati, carinis fortibus (in anfr. superioribus duabus , 

 in idtiono senis) instructi, lineis incrementi tenuissimis sculpti ; 

 apertura ovata, longit. totius g haud cequans ; peristoma con- 

 tinuum, margine externo vix incrassato, columellari dilatato, 

 rejlexo, rimam umbilicalem formante. 

 Longit. 2| millim., diam. Ig. 



This species closely resembles B. perfecfa in form. It is, however, 

 a little larger, is not spotted, and has seven keels on the body-whorl 

 instead of five ; of these, the one nearest the suture is very fine and 

 thread-like, the next two, which also pass up the spire, are strong 

 and prominent, and the remaining four gradually lessen in thickness, 

 the lowermost being very inconspicuous. 



The nucleus of this species is also different from that ofR.perfecta, 

 and the outer lip is not thickened in the same manner. 



RiSSOA FENESTRATA, KraUSS. 



Hab. Cape of Good Hope. 



