160 PROF. P. M. DUKCAlSr's REVISION OF TUE 



and of pillars. Actinal tubercles larger tliau the abactinal and 

 tlie spines also, those of the dorsum are clavate. 



Fossil. Tertiary : Europe, Africa, Asia. 



Becent. Japan, E. coast of Africa, Eed Sea, Madagascar, Java, 

 Philippines, Kew Caledonia. 



Grenus Eistcope, Agassiz, 1841, Monogr. d'Ech. viv. etfoss. livr. 2, 

 Les Scufelles, p. 45. Michelin, 1851, Bev. et Mag. Zool. 

 France,-p. 99. LUtken, 1863 (pub. 1864), Vid. Medd.f. Nat. 

 For. Kjohenh. pp. Ill and 133. Verrill, 1867, JSTotes 07i 

 Badiata, p. 309. A. Agassiz, 1872-4, Bevision, pp. 126, 

 324, 544. Loven, 1874, Etudes, p. 47. 

 Test moderate and large, very depressed, slightly arched dor- 

 sally, flat actinally ; marginal outline variable, circular, elliptical, 

 ovoid or subpeiitagonal, may be broader than long or the reverse, 

 more or less truncated behiud. A broad notch of greater or less 

 length, or a luuule in the median lines of the ambulacra, and a 

 lunule in the posterior interradium. 



Apical system central, or excentric in front ; madreporite more 

 or less stellate in outline, the five genital pores outside of it ; the 

 radial plates small and the pores minute on its sides. 



Ambulacra divisible into a biv'um and trivium ; the posterior 

 petaloid parts the longest, very nearly closing, with very broad 

 poriferous zones ; inner pores large, others small in very narrow 

 grooves. Actinally the ambulacral grooves are perforated, bi- 

 furcating and branching towards the margin. The second ambu- 

 lacral plates of all the zones are large, and unite so as to form a 

 ring around the peristome, which is composed of ten small ambu- 

 lacral plates and five interradial plates. 



Interradia very narrow abactinally, the highest pair of plates 

 narrow and including the genital pore in the median suture ; 

 actinally discontinuous, a single peristomial plate to each area. 



Peristome small, subpentagonal ; a single half-hidden spheri- 

 dium in each ambulacrum. Periproct small, between the posterior 

 lunule and the peristome, or entering the lunule. 



Inside, the test is very cellular, and there is a more or less 

 continuous area with pillars and partitions, some concentric or 

 radiating from many points near the edge within ; cellular struc- 

 ture separating the poriferous zones of the ambulacra from the 

 intestinal tract and reaching inwards ; a corresponding structure 

 becoming lamellar in the interporif erous areas, aud another sur- 

 rounding the jaws. 



