HOLOPXEUSTES. 483 



The poriferous zone is narrow ; buccal membrane with a few small plates 

 irregularly scattered over the surface. It is very probable that this species 

 will eventually form the type of a new genus intermediate between Salmaeis 

 and Amblypneustes; unfortunately I have but a single specimen, and until 

 there is more abundant material this species is temporarily placed with 

 Amblypneustes, which is its nearest ally. 



(AMBLYPNEUSTES.) Holo:pneustes. 



Holopneustes Agass., 1841, Mon. Scut. 



The ambulacra are broader than the interambulacra, owing to the extraor- 

 dinary lateral development of the poriferous zone. Each zone is flanked 

 by a regular vertical row of pores, the intermediate space is closely packed 

 with pores arranged apparently irregularly, though in reality the irregularity 

 is due only to an unusual lateral expansion of the central plate. General 

 facies that of Amblypneustes. Lutken unites the genus with Ambl}-pneustes. 

 I cannot agree with him in this, as the true Amblj-pneustes, no matter how 

 the pores are arranged, — in three vertical rows, as in Tripneustes, or tri- 

 geminate, — never have more than three regular vertical rows, so that I am 

 inclined to consider this group as a subgenus of Amblypneustes. The actino- 

 stome is small, has no cuts. The spines and the abactinal system are essen- 

 tially that of Amblypneustes. Teeth broad, with a low inner ridge. Spines 

 short, moderately stout, longitudinally striated, and swollen at the extremity. 



Holopneustes inflatus 



! Ambhjimeustes inflatus Lutk., 1872, in A. Ag., Bull. M. C. Z., HI. 

 I Holopneustes inflatus A. Ac, 1872, Bull. M. C. Z., III. 



Test moderately stout, nearly spherical ; poriferous zone more than equal- 

 ling in width the median ambulacral region, proportionally somewhat nar- 

 rower than in H. porosissimus, the pores arranged in three well-marked 

 vertical rows, — the inner and outer quite regular, the middle somewhat undu- 

 lating and disconnected. One very regular vertical row of small secondaries 



