GENERA AND GBOUPS OE THE ECHINOIDEA. 113 



Apical system small, slightly projecting ; basal plates united ; 

 the genital pores at the adoral angle large or small according to 

 sex ; radial plates excluded, the pore visible from above ; madre- 

 porite defined, openings circular ; periproct with a crowd of small 

 plates each with a miliary. Coronal plates numierous, low, 

 broad. 



Ambulacra broad, with rows of very small plain, faintly crenulate 

 tubercles placed so as to leave a more or less definite median 

 space, where there are pedicellariae but no primary tubercles. 

 Poriferous zones wide, with or without miliaries and secondaries ; 

 pores in oblique triple pairs, close vertically, the innermost pair 

 is the adoral of a triplet. Plates numerous, compound ; consisting, 

 when large, of a large adoral primary plate, a small middle demi- 

 plate, and a larger aboral demi-plate, which sometimes, especially 

 abactinally in the test, becomes a primary plate. 



Interradia with low broad plates ; tubercles resembling those 

 of the ambulacra, varying in vertical number and obliquity ; a 

 greater or less bare median space. 



Sutures of both areas visible, narrow ; minute shallow pits at 

 the median angles, and sometimes along the median sutures ; 

 ornamentation plain, or of vertical zigzags of broad lines or of 

 curved lines crossing the median area. Dowelling abundant. 



Peristome variable in size, usually small ; branchial incisions 

 small. Perignathic ridges low, processes slender, high ; foramen 

 triangular or broad. Spines slender, short, striated, distant. 



Becent. Australian and New Zealand seas, Eiji. (Cape of 

 Grood Hope ?) 



Amhlypneustes griseus is a very erratic species ; and it is evident 

 that A. Agassiz is correct in relegating A. pentagonus to a 

 separate genus. 



Grenus Goniopneustes, gen. nov. 



Test thin, nearly globular, but pentagonal in circumferential 

 outline, the ambulacra projecting beyond the concave interradia. 

 Coronal plates high and few. 



Apical system delicate, with the madreporite in a large basal 

 plate; other basals pointed, narrow, pentagonal; some radial plates 

 enter the ring. 



Ambulacra with two vertical rows of plain primary tubercles, 

 with raised scrobicules ; median spaces more or less bare ; pori- 

 ferous zones narrow ; pairs of pores in triplets. 



LINN. JOURN. — ZOOLOer, VOL. XXIII. 8 



