174 



PAXAMIC DEEP SEA ECHINI. 



In Palaeobrissus 1 the ambulacra] plates widen very regularly from the 

 apex to the ambitus, as in Argopatagus, without the break forming the ill- 

 defined petaloids of Genicopatagus. The 

 pores, however, form diverging lines and 

 increase regularly in size, much as they do 

 in Paleopneustes. In the apical system of 

 Palaeobrissus the anterior genitals are united 

 in one plate carrying the madreporic body, 

 and the posterior genital plates are distinct, 

 though in contact, — a combination which has 

 not been noticed in other Spatangoids. 



From the position of the anal system and 

 the structure of the actinostome, Genicopata- 

 gus has somewhat the furies of Paleopneustes, while the outline of Phrisso- 

 cystis and Argopatagus are quite similar, Fig. 255. 



37 mm. 



Fio. 254. Genicopatagus affinis 



1 AjRGOPATAGUS VITRErs. Dorsal. 48 mm.? 

 3 PALEOPNEUSTKS UYSTHIX. Ventral. 153mm. 



•_' Genicopatagus affixis. Dorsal. 37 mm. 



4 PHBISSOCYSTIS \( 1 I.KATA. Dorsal. 120mm. 



Blake" Echini, PI. XXIV. tigs. 10-12. 



