146 



PAKA.MIC DEEP SEA ECHINI. 



f>'2 mm. 



Fig. 212. Echinocbepis retk.f.ka. 



The sternum and adjoining episternal plates (PI. 68, fig. s) of the odd 

 posterior interambulacruin are thickly packed with primary tubercles, 

 Fig. 212; these plates form a slight keel on 

 the actinal side when the test is seen facing 

 the anal extremity (PI. 67, figs. /, ,;). 



As in Pourtalesia the trivium is separated 

 from the bivinm, Fig. 21o, by the abactinal 

 plates of the lateral posterior ambulacra (Pis. 

 67, fig. :.'; 68, figs. .'. j ; 69, figs. .:, {), and by 

 additional intercalated plates, all of which are 

 larger than the abactinal terminal plates of the 

 odd interambulacrum. 



There are four genital openings ; the ma- 

 dreporite extends over two of the plates which have become soldered, and 

 carries the anterior genitals. Against this, the intercalated plates (PI. 69, 



figs. 3, 4), the ambulacra, and in- 

 terambulacra of the trivium abut. 

 The four genital organs form small 

 clusters hanging from a tube per- 

 haps 15 mm. in length. As is seen 

 in E. cuneaia, four of the genitals 

 have united and are covered by the 

 madreporic body. 1 



The ocular plate can only be 

 traced in the odd anterior ambula- 

 crum (PI. 69, figs. ./, .j). In the 

 21 crowding due to the intrusion of the 

 intercalated and interamhulacral 

 plates between the bivinm and the 

 trivium they have been pushed out 

 of place or resorbed. The fragments 

 of the abactinal system showed great 

 irregularity in the number and posi- 

 tion of the interambulacral and intercalated plates separating the bivinm 

 and the trivium. See also those of E. cnneata, 2 where the separation is 

 made by one plate, which differs from any I have seen in E. setigera? 



1 L,ove"n, Pourtalesia. I'l VII, fig 54. « " Challeuger " Echinoidea, PI. XXVTT, fig. 9. 



3 Loven, Pourtalesia, PI. VII, fig. 54. 



21 



* v 5 a 



92 mm. 



Fig. 213. Echinocbepis settgeba. 



