136 



PANAMIC DEEP SEA ECHINI. 



anterior interambulacra are larger (PI. 57, fig. ,5). In this respect P. Tanneri 

 is more closely allied to P. carinaia, Fig. 197, in which, according to Loven, 1 

 the primordial plates of the posterior interambulacra and the labium occupy 

 much the same position they do in P. Tanneri. A similar arrangement is 

 found in P. ceratopt/ga and E. cuneatar 



Fin. 196. 



Hi mm. 

 POI BTALESIA TaXXERI 



FlG. 1!'". P. CARINATA. 



After Loven. 



The actinal system of P. Tanneri, Fig. 170, is circular (Pis. 56, fig. 4; 

 57, figs. ?, 3) ; the outer belt is covered by delicate elongated plates forming 

 three or four irregularly concentric rows. The central part of the actinal 

 system is bare. The course of the odd anterior ambulacrum (Pis. 56, figs. 



FlO. 1US. l'ul RTAI.ESIA JeFFREYSI. 



After Loven. 



la' I ' & V 



16 mm. 



Fig. 199. P. Tanneri. 



1—4; 57, fig. 2) is specially well seen from the interior view of the test 



(PI. 57, fig. .'), which shows t he rapid widening and arching of the ambu- 



lacral plates to form the deep anterior actinal ambulacral groove. The 



1 Loven. Pourtalesia, PI. VI, figs. 42-4 1. - Id., PI. VII. figs. 48, 53. 



