114 PEor. p. M. Duncan's revision of the 



Interradia with tubercles resembling those of the ambulacra. 



Peristome small. Spines of primary tubercles of great size. 



Recent. Mauritius. 



The above diagnosis is abstracted from the description of the 

 solitary sjjecimen of Amhlypneustes pentagonus, A. Agassiz 

 (Eevision, p. 482). 



Genus Holopneustes, Agassiz, 1841, Ecli. viv. etfoss., Valentin, 

 Anat. Gen. Ech., Preface, p. 9. A. Agassiz, 1872-74, Revi- 

 sion, p. 483. Bell, 1880, Froc. Zool. Soc. p. 439. Duncan, 

 1888, Ann. ^ Mag. Nat, Hist. ser. 6, vol. i. pi. xi. figs. 14-16, 

 p. 117. 



Test moderately stout or tbin, globular or prolately spheroidal, 

 or subconical above the tumid circular ambitus. Interradial 

 coronal plates numerous ; ambulacral plates very numerous. 



Apical system projecting, stout ; basal plates broad, subequal ; 

 radial plates excluded, the pore visible from above. 



Ambulacra broader than the interradia ; and the poriferous 

 zone usually broader than the interporiferous area, slightly de- 

 pressed, with secondary tubercles and granules ; pairs of pores 

 close vertically, irregularly distant horizontally, triserial or poly- 

 serial ; an inner and an outer regular vertical series of pairs, and a 

 confused middle series. The middle series of pairs of pores are in 

 the aboral components of as many compound plates ; the pairs of 

 the outer vertical row are those of middle component plates, and 

 the inner series of pairs are placed in adoral primary compo- 

 nents which are often excluded from the ambulacro -interradial 

 suture. 



Tubercles of the interporiferous areas small, plain, variable in 

 number, more or less median space exposed. Interradia with 

 transverse rows of primaries and secondary plain tubercles ; median 

 area variable. 



Sutures sunken, linear ; pits at the angles small, but distinct, 

 shallow ; plates dowelled. 



Peristome small, pentagonal, with small but distinct branchial 

 incisions. Spines short, striated, may be swollen at the free 

 end. 



Recent. Australian seas. 



The next genus links the TemnopleuridsB and the Echinidse, 

 but it is placed as incertce sedis. 



