I 



130 



PANAMIC DEEP SEA ECHINI. 



is more like the groove of P. Jeffre//si. In Echinocrepis setigera, Fig. 185, 

 the groove is over a fourth of the test (PI. 66, fig. 7), as in E. cuneata^ 

 also, and in Spaiagocystis Challerif/erP it is nearly half the length, Fig. 186. 



20 mm. 30 mm. 80 mm. 



Fig. 187. 1 Pi,exechikus cinctus. 2 Urechinus Naresianus. 3 U. gigaxtecs. 



The position of the actinostome in the Urechinidoe is more central than 

 in the Pourtalesia?, even than in such a genus as Plexechinus, Fig. 187, i; 

 in Cystechiniis Wyvillii and C. Zoveni the actinostome is also more excentric 

 than in Pilemateclunus Rathbuni, Fig. 188, 3. 



18 ram. 



S3 mm. 



92 mm. 



Fig. 188. 1 Cystecuixcs Wyvillii. 2 C Love.m. 3 P. Rathbum. 



Is there not in the Clypeastroids something analogous to the intrusion 

 of the lateral posterior interambulacra betwoen the labium and sternum 



» "Challenger" Eehinoidea, PI. XXXV\ fig. 10. ^ jj. pi. XXVI*. fig. 2. 



