266 PBOF. p. M. dtjncan's eetision of the 



TV. Division Ap etala. 



Spatangoidea with flush, apetalous, and generally uniporous, 

 ambulacra, similar or may be diverse ; plates high, few, often 

 hexagonal. Apical system usually ethmophract ; phyllodian pedi- 

 cels with a simple marginal row of filaments. Fascioles present 



or absent. 



Section Adetes. 



Genus Genicopatagus. 

 PalcEohrissus. 

 Section Prymnadetes. 

 Genus Aceste. 

 A'erope. 

 Section Pkymnodesmia. 

 Gtniis Ovulaster. 



PalcBOtropus. 

 Homolampas. 

 Argopatagus. 

 Cleistechinus, 



TV. Division Ap etala. 

 Section Adetes. ("Without fascioles.) 



Genus Gtenicopatagus, A. Agassiz, 1879, Proc. Am. Acad. xiv. 

 p. 210; 1881, Report on the 'Challenger^ JEchini, p. 161, 

 Loven, 1883, Pourtalesia, pp. 60, 76. 



The test is moderate in size, circular in outline at the ambitus, 

 rather flat and depending posteriorly actinally, tumid above, 

 being highest and sloping roundly and sharply posteriorly and 

 gradually in front, nearly hemispherical in outline at the sides 

 and over the top. The apex of tbe test is far back, and there is 

 the apical system. 



Apical system with three perforated basal plates and a large 

 right antero-lateral basal with the madreporite, without a pore 

 for the genital duct, and a small accessory imperforate plate, 

 possibly a posterior basal, placed close to the left posterior 

 basal. The madreporite is restricted to the anterior part of the 

 right anterior basal, which separates the posterior basals and the 

 posterior radials. Eadial plates well developed and perforated, 

 their pore being visible from above. 



