GENERA AND GEOUPS OP THE ECHINOIDEA. 121 



Subfamily Polyporinee (p. 116). 



Grenus Steongtlocenteottjs, Brandt, 1834, Prodr. Descr. Anim., 



Bee. des Actes de VAcad. St. Be'tersb. (Additions), p. 265. 



Loven, JEtudes, 1874, p. 21 {as Toxopneustes). A. Agassiz, 



1872-73, Bevision, pp. 276 & 438. 



Syn. Loxechinus, Desor, 1858 ; Toxopneustes, Agass., 1841 



(pars) ; Heterocidaris, Desm., 1846 (pars) ; Toxocidaris, A. Agass., 



1863 ; AntJiocidaris, Liitk., 1864 ; Eiirechinus, Verr., 1866. 



Test moderate and large in size, broader tban bigb, circular or 

 snbpentagonal in tumid ambital outline, swollen, subcorneal, 

 depressed dorsally, slightly tumid around the actinostome. Co- 

 ronal plates numerous. 



Apical system large ; madreporite large, in the usual basal plate, 

 which is the largest ; other basal plates unequal in size, all with 

 some small secondary tubercles; radial plates broad adorally, 

 some entering the periproctal ring. Periproct subcircular, with 

 numerous crowded, minutely tuberculate plates. 



Ambulacra straight, broad at the ambitus and peristome ; 

 poriferous zones broad ; pairs of pores in oblique arcs, or almost 

 in transverse, slightly bent series of from four to eight or ten 

 pairs, polyserial and crowded actinally. Plates high, compound ; 

 the adoral component a large primary plate with its pair of pores 

 the remotest from the interradium ; the aboral plate a small 

 primary with an oblique adoral suture, its pair of pores not 

 quite so remote from the interradium as the adoral pair; other 

 plates demi-plates, with their pairs of pores gradually dimi- 

 nishing in distance from the interradium, from above actinally. 

 Interporiferous area with two vertical rows of imperforate plain 

 non-scrobiculate primary tubercles, wide apart at the ambitus, 

 narrowed and close and small actinally ; vertical rows of secon- 

 daries and miliaries between and at the sides, some intruding 

 upon the poriferous zones and separating the arcs more or 

 less. 



Interradia with high ambital and low actinal plates; two 

 vertical rows of primary tubercles similar in structure to, but 

 larger than, those of the ambulacra, and four or more vertical 

 rows of secondary tubercles ; granules somewhat regularly placed ; 

 areas much narrower actinally than those of the ambulacra. 



