156 



PANAMIC DEEP SEA ECHINI. 



To which of the series the intercalated plates belong, it seems impossible 

 to determine. By analogy we might take this central plate to represent 

 the two contiguous ocular plates of Cystechinus (PI. 79, lig. ..'), or of the 

 specimen of U. Naresianus figured by Lovrn, 1 which has two oculars, 

 Fig. 226, occupying the place of the single central plate in U. giganteus. 



In Urechinus Naresianus, PI. 74, tig. ;. the oculars of the trivium together 

 with the madreporic genital form a connected series separated from the bivium 



Fig. 226. U. Naresianus. 



After Loven. 



Inside view. 30 mm. 



Fig. 227. Ubechintjs Xauesianus 



by four small intercalated plates and the two posterior lateral genitals, which 

 in the specimen of 13 mm. are not perforate. In a still older specimen 

 30 mm. in length, Fig. 227 (PI. 60, figs. /,, .;), the abactinal plates of 

 the anterior zones of the posterior pair of interambnlacra separate the 

 bivium from the trivium, as well as a couple of small intercalated plates 

 adjoining the central ocular plates and those of the bivium, the posi- 

 tion of which is doubtful. The great size of the posterior genitals of 

 U. giganteus, Fig. 224, is in marked contrast to the small genital plates 

 of U. Naresianus r 



1 rourtalesia, PI. XXI, fig. 242. 



- M. de Meijere has figured an interesting Ananchytid : Sternopneustes (Sternopnettstes relicius de 

 Meijere, 1. c. p. 117); it has much the outline of Palenpneusles cristatus, the abactinal system and 

 sternum of Urechinus, but its actinal system is more like that of llomolampas, with a slightly 



