134 PEOP. p. M. Duncan's eevision of the 



slight. Few buccal plates. Tubercles rather large, with secon- 

 daries ; bare median areas slight. 

 Mecent. New Zealand. 



Genus incertce sedis. 



The following diagnosis is taken from tlie description of the 

 solitary species so well described by Agassiz in the Eeport on 

 the * Challenger ' Echini : — 



Gi-enus Peionechintjs, A. Agassiz, 1879, Proc. Amer. Acad. vol. 

 xiv. p. 202; IS^l, Report on '■Challenger^ Echini, p. 109, 

 pis. vi. A. & xl. 



Test thin, small, circular in the tumid marginal outline, 

 depressed. 



Apical system large and compact ; basal plates broad, angular, 

 and with secondary tubercles on their periproctal edge ; radial 

 plates large, projecting much beyond the basal plates, pore 

 adoral. 



Ambulacra narrow ; the poriferous zones rather broad, with 

 two pairs of pores to a plate, in simple vertical series. 



Interradia with two vertical rows of large plain tubercles 

 placed near the median suture and sparely distributed granules 

 and small tubercles. Interradia with the coronal plates only 

 slightly higher than those of the ambulacra, a primary tubercle 

 on each about the dimensions of an ambulacral primary, sur- 

 rounded by some secondary tubercles. Pedicellarise large-headed. 



Spines prominently serrated and rather flat. 



Peristome with slight branchial incisions ; five pairs of large 

 buccal plates, and only one large tentacle to a pair of plates. 



Becent. Philij)pines and Australia, 700 to 1070 fathoms. 



It is impossible to place this genus satisfactorily, so it must 

 remain as incertce sedis. 



