140 HAWAIIAN AND OTHER PACIFIC ECHINI. 



Phryssocystis. 



A. Agassiz, 1898. Bull. M. C. Z., 32, p. 80. 



Type, Phryssocystis aculeata A. Agassiz, 1898. Loc. cit. 



This genus is known only from fragments taken by the Albatross, once 

 near Cocos Island and once at an unknown station supposedly in the Hawaiian 

 Islands. No whole specimens were secured, the test being exceptionally thin 

 and fragile, but from a study of the fragments Mr. Agassiz worked out the 

 form and structure of the test and I found a number of pedicellariae. The 

 ophicephalous pedicellariae are particularly remarkable and show the close 

 relationship of this genus to Argopatagus, the only other genus of Echini known 

 to have such curious pedicellariae. In view of what I have learned in regard 

 to growth-changes in Palaeotropus, it is quite possible that Phryssocystis will 

 ultimately prove to be the adult of Argopatagus. 



Key to the Species of Phryssocystis. 



Primary tubercles on each abactinal plate in mid-zone, 2-8; color yellowish brown . . aculeata. 

 Primary tubercles on each abactinal plate in mid-zone, 8-12; color deep red-brown . . multispina. 



Phryssocystis aculeata. 



A. Agassiz, 1898. Bull. M. C. Z., 32, p. 80. 



Mr. Agassiz has so fully described and beautifully figured this species, 

 I need only speak of the pedicellariae. I have failed to find the characteristic 

 pedicellariae but have no doubt this is due to the scanty available material. 

 The tridentate and triphyllous were both found but are not abundant on the 

 fragments at hand. These pedicellariae are very similar to those of the follow- 

 ing species and no constant differences were noted. The only known specimens 

 of aculeata were taken east of Cocos Island, Eastern Pacific Ocean, in 1067 fms. 

 but reached the surface in fragments. 



Phryssocystis multispina. 



A. Agassiz and Clark, 1907. Bull. M. C. Z., 50, p. 263. 



Plates 145, figs. 7-1$; 151, figs. 1-4- 



It is greatly to be regretted that neither the place nor the depth at which 

 this interesting species was taken are known. The jar containing the frag- 



