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



^ suheequmis ; peristoma tenue, margine columellari leviter 

 reflexo, superne lahro callo tenui juncto. 

 Longit. 2 millim., diam. 1. 



This species has more convex whorls than R. 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 pallide fuscescens ; anfractus 

 4, convexi, primus et secundus spiraliter striatic sequentes liris 

 transversis {in anfr. p>emdtimo circiter 3, in ultimo 8-9) in- 

 structi ; apertura rotunde ovata, longit. totius | pauIo minor ; 

 peristoma continuum, vix incrassatum, margine columellari 

 anguste rejiexo. 



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, solidiuscula, alha, imperforata, nit Ida ; anfractus 

 4, convexiusadi, sutura mediocriter profunda, paido obliqua 

 sejuncti, spircditer suhstriati ,• apertura rotunde ovata, superne 

 acuminata, longit. totius 5 paxdo superans ; peristoma continuum^ 

 leviter incrassatum, margine columellari dilatato. 



Longit. I3 millim., diam. |. 



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

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

 by the aid of a microscope. 



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



Testa hrevis, turrita, alha, vix rimata ; anfractus b, primi duo 

 convexi, laves vel spiraliter tenuiter striati, cceten superne 

 tahulati, anijulati, carinisfortilms {in anfr. svperioribus duabus, 

 in idtimo senis) instructi, lineis incrementi tenuissimis sculpti ; 

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

 tinuum, marqine externo vix incrassato, columellari dilatato, 

 rejiexo, rimam umbilicalem formante. 

 Longit. 2g millim., diam. 1|. 



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

 a little lar<>;er, 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 o^R. perfecta, 

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



RiSSOA FENESTRATA, KraUSS. 



Hab, Cape of Good Hope. 



