16it PROF. p. M. DTTNCAN's REVISION OF THE 



several sliort digitations, varying in length at the sides and pos- 

 teriorly, witli or without incisions, and two anterior lunules ; 

 slightly tumid dorsally, and flat or concave actiually. 



Apical system small, central, tumid, stellate or not ; radial 

 plates small and with minute pores at the end of the limbs of the 

 star ; the four large genital pores within the system, rather close 

 and separated by part of the madreporite or in grooves. Madre- 

 porite central and extending outwards ; sutures not visible ; fifth 

 genital pore absent. 



Ambulacra well developed, subequal, but divisible into bivium 

 and trivium, long, subpetaloid, open distally, where the pores di- 

 verge and are continued irregularly to the margin ; poriferous 

 zones broad ; pores large, except quite apically, with or without 

 a line of intermediate minute perforations. In well-defined 

 grooves at the peristome, perforated minutely, ending in a peri- 

 storaial projection where there are large pores, grooves bifurcate 

 into the digitations or not and in front. Spheridia, one in each 

 peristomial groove, half covered. 



Interradia very narrow at the apex and with one plate there ; 

 disconnected actinally, except in the posterior area and sometimes 

 in area 3, on account of the dimensions of plates 2 of the ambu- 

 lacra external to the peristomial series. 



Peristome small, central, subpentagonal, with five slightly 

 projecting ambulacral processes, surrounded by ambulacral and 

 interradial plates. 



Jaws short, small ; teetb superior ; perignathic processes inter- 

 radial, single, small, low, hollow towards the pyramids. 



Periproct small, circular, between the peristome and the digi- 

 tations. Tubercles of the actinal surface very uniform, small and 

 close ; similar distribution abactinally. 



Internal dissepiments wanting centrally ; no septum between 

 the ambulacral and intestinal areas ; some needles in the digi- 

 tations and extending inwards as columns or layers, but scanty 

 in arrangement. 



With or without two anterior lunules. 



Mecent. W. coast of Africa and Cape Verde Islands. 



There are two sections of this small genus — (1) with lunules 

 and intermediate ambulacral pores, the type of which is B.Augusti^ 

 Klein ; (2) without lunules, R. Bumphii, Klein. 



