aEIfEEA AND GR0T7PS OP THE ECHINOIDEA. 141 



perignathic girdle with rather tall interradial ridges and jaws *. 

 Periproct inframargiual, oval and longitudinal. 



Ornamentation of the ambulacra similar to that of the inter- 

 radia, small, very equal, of small perforate and crenulate primaries 

 in sunken scrobicules and intermediate granular epistroma ; costse 

 ornamented. 



Fossil. Cretaceous : Europe (?). Eocene : Europe, Africa, 

 Asia f. 



Genera incert<je sedis. 



G-enus GtAlekoptgus, Cotteaic, 1856, Bull. Soc. Geol. de France, 

 ser. 2, vol. xiii. p. 648, & 1858-9, vol. zvi. p. 289. 



Syn. Galeopygtos, Desor, Synopsis, 1858, p. 167; Centropygus, 

 Ebray. 



Large depressed Urchins, circular at the slightly swollen margin, 

 except posteriorly, wh ere the edge of the test is thin and trun- 

 cated. 



Apical system central, or excentric in front, closed in front 

 and open behind, with four basal plates contiguous and perfo- 

 rated; the madreporite in the usual basal, which is the largest. 

 The anterior and the right antero-lateral radial plates outside, 

 the others in contact with the periproctal groove. A groove con- 

 taining the periproct entering the apical system and separating the 

 posterior radial plates, the postero-lateral basals, and reaching 

 the left anterior radial plate and the anterior pair of basals. The 

 groove passes down to the posterior truncation, and the periproct 

 is partly within and partly outside the apical system. 



Ambulacra narrow, flush, straight, except the postero-lateral, 

 which are more or less curved abactinally. Pairs of pores in 

 simple series. Taberculation of the test small, rather distant, 

 homogeneous. Peristome central, decagonal, with branchial in- 

 cisions. Spines subulate, striated, short. Neither perignathic 

 girdle nor jaws have been seen. 



Fossil. Oolite : England, Europe. 



* A specimen in the British Museum shows the perignathic girdle rubbed 

 down, and a vertical section in another specimen shows the interradial projec- 

 tion or ridge. There is no process connected with an ambulacrum, but the 

 interradial ridges are well developed. The girdle resembles that of Biscoidea 

 somewhat. 



t The genus Phyllocl^peus, De Loriol, absorbs the old Conociypei with floscelles 

 and no teeth. 



