Q-ElfEEA AND GROUPS OF THE ECHINOIDEA. 103 



G-enus Zeuglopleurus, Gregory, 1889, Ann. Sj' Mag. Nat. Hist. 

 ser. 6, vol. iii. p. 494. 



Syn. JEcliinopsis (pars) ; EcMnocyphus (pars) ; Glycocyplius 

 (pars). 



Test small, globular, depressed below, sligbtly conical above ; 

 sides tumid. Epistroma well developed. 



Apical disk somewbat solid, tbe two postero-lateral radial plates 

 enter the periproctal ring ; tbe antero-lateral pair of basal plates 

 meet the adjoining basals, and thus the antero-lateral and anterior 

 radial plates are excluded from the ring, while the periproct is 

 pushed towards the posterior end; the posterior basal is very 

 narrow. All plates perforated by the madreporite. 



Ambulacra somewhat narrow and straight. Each bears two 

 rows of primary tubercles, which are slightly smaller than those 

 of the interradia, and are crenulate, imperforate, and surrounded 

 by small scrobicules, broken by series of radiating costulate 

 ridges which unite with those of the adjoining plates above and 

 below ; the rest of the plate with miliary granules arranged with 

 some regularity. The horizontal sutures are notched with 

 grooves much as in GlypliocypJius, which affect especially the 

 adoral edge of the plate, so that the lower plate projects above 

 the upper one. In the poriferous zones the pairs of pores are in 

 single and nearly straight vertical rows ; the plates nearest the 

 apex are primaries ; bat proceeding actinally they become fused 

 to compound j)lates of two or three primaries ; a single primary 

 is often intercalated between two compound plates. 



Interradia one and a half times as wide as the ambulacra ; the 

 epistroma similar to that upon the ambulacral plates, but more 

 developed. A single vertical row of primary tubercles on each 

 side of each, interradium ; the tubercles larger than those of the 

 ambulacra and connected by costulate ridges, and the rest of the 

 plate is covered with very close miliary granules ; a small row of 

 secondary tubercles may be developed in the aboral external 

 corner of each plate. Tubercles imperforate and crenulate. 



Peristome about equal to the apical disk in size ; branchial 

 slits small. 



Fossil. Cretaceous : England, Europe. 



The type is Zeucjlopletirus costulatus, Grreg. 



