128 



PANAMIC DEEP SEA ECHINI. 



There are. great differences in the number of plates of the odd an- 

 terior ambulacrum: in P. Jefreysi we find thirteen to fifteen pairs, Fig. 

 178 ; in P. Tanneri twelve, Fig. 179 ; in other genera of Pourtalesiae, as in 



ppi. 



43 mm. 



Fig. 177 a . Spatagooystis Oham.enueki. 



Fl(i. 17S. Pol UTALESIA JEFFBEYSI. 

 After Loven. 



Echinocrepis, tliere are twenty-one to twenty-two, Fig. 180 ; and in Spatago- 

 cystis, sixteen pairs, Fig. 181. The number of the plates is due mainly to 

 the length of the actinal pouch in those genera. These differences are 

 well shown on comparing the profiles of the actinal pouches of P. Jeffreysi? 

 of P. cannula; 2 Fig. 182, of P. Tanneri (PI. 57, fig. ?), of P. hispida, 3 of 



10 mm. 



Fig. 179. P. Taxnejii 



92 mm. 



Fig. ISO. Echinocbepis setigeba. 



48 mm. 

 Fig. 181. Spataoocvstis Challengeri 



P. ceratopyga? of Echinocrepis setigera (PI. 60, fig. -'), and Spatagoci/stis 

 ( 'hallengeri { PI. 71. fig. -'). These profiles differ greatly in outline, especially 

 in the angle formed by the groove with the actinal system, as well as 



1 Loven, Pourtalesia, PI. Ill, fig. 12. 



« Loven, PI. VI, fig. 45; ••Challenger" Echinoidea, PI. XXVIII", fig. 11. 



3 "Challenger" Echinoidea, PI. XXII, fig. 8. 



« "Challenger" Echinoidea, PI. XXVIII, fig. 5. 



