242 PEOF. p. M. DUNCAlsr S REVISION OP THE 



Sci. Nat. ser. 3, vol. viii. p. 12. Besor, 1858, Synopsis, 

 p. 403. J^. ^^fflms!, 1872, ^evmow, pp.96, 856, 596. JBolau, 

 1872, Spatang. d. Rami. Mus. p. 11. Loven, 1874, Etudes, 

 figs. 43, 122, 123, 202-204. {Amended.) 



Syn. Brissomorpha, Laube ; Heterobrissus, Manz. & Mazz. 



Test moderate and large, ovoid in tumid marginal outline and 

 narrowest posteriorly, regularly convex but depressed dorsally, 

 tumid and convex actinally, except in front of tbe peristome, 

 truncated obliquely downwards and forwards at the posterior 

 surface below tbe ambitus, or straight ; no anterior groove be- 

 yond some slight local depression. 



Apical system excentric in front, the four basal plates perfor- 

 ated, and the madreporite extending from the right anterior basal, 

 centrally, and thence posteriorly so as to separate the postero- 

 lateral basal and radial plates. 



Ambulacra diverse, the anterior flush or in a very slight de- 

 pression ; the pairs of pores small and closest abactinally ; antero- 

 lateral ambulacra very divergent, nearly forming a straight 

 transverse line, in grooves of varying depth, the petaloid parts 

 shorter than the corresponding parts of the postero-lateral am- 

 bulacra, which are comparatively close together; the pores of 

 the inner rows of a round or slightly elongate shape, and those of 

 the outer rows elongate ; petals with narrow interporiferous areas 

 and the pairs tending to close, the distal ends of the postero- 

 lateral petals diverging outwards or not. Actinally the postero- 

 lateral ambulacra are very narrow and long, with few single 

 pores, more numerous at the peristome. 



luterradia large actinally, with very large second and third 

 plates ; normal heteronomy of interradium I. 



Peristome excentric in front, semilunar, with a large projecting 

 posterior labrum, behind which is a broad amphisternum ; sphe- 

 ridia numerous. Periproct in the posterior truncation, large. 



A peripetalous fasciole entering the lateral iuterradia consider- 

 ably, sinuous more or less; a subanal fasciole surrounding a 

 broad area including six ambulacral plates, the upper part of the 

 fasciole concave. Ornamentation of very crowded almost homo- 

 geneous tubercles abactinally, and of slightly larger tubercles 

 actinally ; rarely some larger tubercles within the peripetalous 

 fasciole. Spines slender, moderately long on the anterior part of 

 the test ; dark brown, yellow, to silver grey. 



