OCULAR AND GENITAL H. \TI.S 



111') 



fig. 97), Astropyga (text-fig. 99), and Chaetodiadema (text-fig. 98). There are M alx-rrapt*, 

 3%. Thirty-one of these have I, V, IV, III insert. This character i- common in ciduritfo an 

 discussed, but is rare in the Centrechinoida, most of the cases seen occurring in tin 

 One aberrant has oculars I, IV insert, V being excluded by the fusion of genital.- 4, ">, a- in text- 

 fig. 144; and one aberrant has V, IV, III insert, evidently an imperfect I. V, IV, III, ami a 

 very rare variant, which, however, is the species character of Str<ii/i/l<>n nlrntiu gibbottws (le\t- 

 fig. 156). While three plates insert is strongly the character of C. selosus, in no case \\ ere . n-ulars 

 I, V, II insert, which is so markedly a character of the Echinidae and Strongylocentroti.lae. 

 It is a remarkable fact that the aberrants of this species fall so definitely in one plan-, I, V. IV. 

 Ill insert, there being only three exceptions to this in the whole 1,278 specimen- examined. 



In Echinothrix calamaris (11 specimens) oculars are all insert in ten, and in one I, V, IV are 

 insert like the typical character of Centrechinus selosus. In Echinothrix diadema (18 specimen- 

 all oculars are insert. 



Centrostephanm asteriscus is interesting as the only Recent species of the CentnohinidM 

 in which the oculars are all exsert in the adult, as they are typically in .luraic -pecie- of the 



99 



TEXT-FIGS. 99-1 01 .-Ocular plate arrangement in Centnvliii.i.hi- im.l 

 99. Astropyga pulvin.,1,, (Lamarck). Gulf of California. Di.,m. '..I mm. 



O. The same, section of ambulacral plates showing .dor.il i,nt,ri,-:ition,andof m.,nlmUrnU 



n. Tokyo, Japan, 55 fath. Db.. 105 mm. R. T. J. Ooi. ,Un, d in- 



sert, genitals, split up, especially vent rally (p. 108). 



