276 PEOF. p. M. dttncan's eevision op the 



Apical system very excentric in front, with four perforated 

 basal plates ; the madreporite large, in tte usual basal, separating 

 tbe lateral basals and tbe posterior radial plates and extending 

 backwards. Eadial plates small and distant. 



Ambulacra apetalous, uniporous ; the anterior ambulacrum is 

 in the anterior groove ; the lateral ambulacra are widely sepa- 

 rated, somewbat waved, widen from the apical system to the 

 ambitus, and thence they become narrow to the peristome. The 

 postero-lateral are very long. The plates are rather high, and 

 the pores are in simple series. The interradia are broad and 

 have large plates. The peristome is semilunar, with more or 

 less rounded angles. There is a thin labrum. 



The plastron is amphisternous, is covered with a tubercular 

 ornamentation, and is bounded laterally by the broad and com- 

 paratively bare actinal plates of the posterior lateral ambulacra. 

 The periproct is small and oval, longest nearly vertically, and 

 situate in the posterior face close above the margin. 



The ornamentation of the interradia abactinally is of a few 

 large primary tubercles much larger than any others, and there 

 are secondary tubercles and miliaries in abundance. Actinally 

 the primaries are smaller, are surrounded by a sunken scro- 

 bicule, and this is also seen from within the test as a sunken 

 "purse," as in Lovenia. The spines of the large tubercles are 

 gigantic and curved, and those of the smaller tubercles are 

 small and curved; those of the actinal side are spathiform. 

 There is a subanal fasciole, which is broad and pentangular, 

 pointed downwards and with indistinct anal branches. The peri- 

 petalous fasciole is inconstant, thin, and incomplete. 



Becent. Straits of Morida, 734-1920 fms. ; coast of Brazil, 

 32-400 fms ; and Pacific, Sandwich Islands to Low Archipelago, 

 2425-2475 fms. 



There are two species. The type was an immature form. 



Genus AKGOPATAaus, ^. Agassiz, 1881, Bep or t on the 'Challenger' 

 Echini, p. 160. 



Test of moderate size, very thin and transparent, truncated 

 in front and bluntly pointed behind, ovoid in marginal outline ; 

 depressed abactinally, flat actinally; broadest in the anterior 

 two thirds, narrower posteriorly. 



