88 PEOF. p. M. Duncan's eevision op the 



in here. Unfortunately the name o£ the genus refers to cuts or 

 sutural impressions upon the tubercles ; and these are not cha- 

 racters of any importance. The fine Sindian forms of GypJiosoma 

 macrostoma, Dune. & Slad., and G. undatum, Dune. & Slad., are 

 now species of Coptosoma. C. Joudi, Peron et Grauth., should 

 enter. 



The genus Microsoma, Cotteau, 1886, Bull. Soc. Zool. de France, 

 vol. xi. p. 715, is so doubtful on account of the bad condition of 

 its specific type, that it is simply recorded. 



Grenus Gatjthieeia, Lambert, 1888, Bull. Soc. d. Sci. Nat. de 

 V Tonne,! Semestre (extrait), p. 7. 



Syn. GypJiosoma (pars). 



Test moderate, subcircular or subpentagonal, moderately 

 tumid. 



Apical system largely developed, pentagonal, with the posterior 

 angle extending well into the corresponding interradium ; the 

 basal plates unequal ; the madreporite in the largest and anterior 

 lateral basal ; the other lateral basals more or less hexagonal, and 

 at the angles of the system the posterior basal forming a narrow 

 rim to the posterior angle, and limiting the posteriorly excentric 

 anus ; radial plates large, all entering and separating the 

 basals. Periproctal area large, and occupied by seven or more 

 hexagonal plates, forming a closed area anterior to the circular 

 anus. 



Spines long, cylindrical, finely striated longitudinally. 



Fossil. Cretaceous : England and Europe. 



In one solitary instance this remarkable apical system has 

 been preserved and described, thanks to M. Lambert; in all 

 others there is only a large vacant space. The genus includes 

 the former GypJiosoma radiatum, Sorginet (subradiatum), 1850, 

 and its synonyms G. simplex and G. spatulifera, Eorbes, and 

 G. perfectum, Cotteau. 



M. Lambert has founded a genus, or rather suggests the recog- 

 nition of a genus of M. Pomel for GypJiosoma pulcJielhim and 

 G. Said and many others. 



In agreeing with M. Lambert's intelligent scheme, it is neces- 

 sary to draw attention to M. Pomel' s definition, which contains 

 the statement that the upper part of the " interambulacrales " is 

 more or less depressed " en gouttiere " in the males, and hollowed 



