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 (PL 79, fig. 3), or of the 

 specimen of U. Naresianus figured by Loven/ which has two oculars, 

 Fig. 226, occupying the place of the single central plate in U. (/iganteus. 



In Urechiiius Naresianus, PI. 74, fig. 7, the oculars of the trivium together 

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



Fio. 226. U. Nabesianus. 



ArTiB Ix)viii. 



Inside view. 30 mm. 



Fig. 227. Urechin'us Nabesiaitus. 



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. ^ j), the abactinal plates of 

 the anterior zones of the posterior pair of interambulacra 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? 



' rourttil.'sia, PI. XXI. fij,'. 212. 



' M.do Meijere has fij^iinul an interesting .\nanchytid: Sternopneiistes (.*N/frHrt;in<t<,<^<'.< rclicttis de 

 Mcijcro, 1. c. p. 117); it has niucli the outline of Paleopneustes crislalu-f, the abactinal system aud 

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



