GEKEUA AND GROUPS OF THE EOHINOTDEA. 259 



Apical system slightly excentric in front, small, with four per- 

 forated basals, compact (?). 



Ambulacra flush with the test, apetalous, diverse, with high 

 plates, broad actinally, and the tentacles tufted around the peri- 

 stome. The anterior ambulacrum narrow and with distant pairs 

 o£ very small pores; the antero-lateral widely divergent, the 

 postero-lateral closer. 



Peristome excentric in front, broad, semilunar, with a pro- 

 jecting posterior lip. Actinal plastron projecting, aud carrying 

 small, short and crowded spines. Periproct small, oval, longitu- 

 dinal, in the posterior truncation of the test, rather high up. 



A peripetalous fasciole, sometimes ill-defined, passing around 

 the apex about midway between it and the ambitus and crossing 

 the ambulacra, without affecting their structure. A well- 

 marked subanal fasciole surrounding the blunt end of the keel. 

 Tubercles small; spines small and short, largest actinally, 

 especially in front of the peristome. 



Becent. Caribbean Sea, 175-233 fathoms. 



The genus Cionoirissus, A. Agassiz, has one species, C. revincltis, 

 which was dredged up in the Arafura Sea by H..M.S. ' Challenger ' 

 from 800 fathoms. The species is described in the Report on 

 the Echinoidea of the ' Challenger,' aud a previous notice both 

 of the species and genus will be found in Proc. Amer. Acad, 

 vol. xiv. p. 206 (1879). 



The generic diagnosis reproduced in the ' Challenger ' Eeport, 

 p. 187 (1881), is mainly comparative. I give a diagnosis which 

 has been abstracted from the description of the species by 

 A. Agassiz, and tested by the drawings (Eeport, p. 187, 

 pi. xxiii.). 



Genus Cionobeisstjs, A. Agassiz, 1879, Proc. Amer. Acad. xiv. 

 p. 14, p. 206 ; 1883, Beport on ' Challenger' Echini, p. 187. 



The test is of moderate size, long, subcylindrical, depressed, 

 ovoid in marginal contour, with a notch in front and a beak 

 behind, tumid above and at the sides, and with a convex actinal 

 surface which is keeled broadly as far as a posterior beak. Test 

 highest in the posterior third, longer than broad, aud about 

 as broad as high ; rounded anteriorly, where there is a broad 



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