250 PEOF. p. M. DUNCAN S RETISION OF THE 



however, M. Cotteau admitted G. Crourdoni, whieli he showed has 

 an imperfect peripetalous fasciole and a test differently shaped 

 from that of the type. 



The researches of A. i\.gassiz regarding the recent species of 

 Brissopsis in the "W. Indies have proved that some forms have 

 divergent antero-lateral ambulacra, especially the young, that 

 there is considerable variation in the depth of the ambital groove, 

 and that during growth the ambulacra are closer. (A. Agassiz, 

 1872-74, Eevision, pi. xix. figs. 8, 9 ; 1883, ' Blake ' Echini, 

 pi. xxvi.) 



The presence of four genital pores in some and three in other 

 species is not important; and the abortion of a duct and its 

 gland is of no more classificatory value in this group than it 

 is iu others. The position of Oyclaster is that of a subgenus. 



Subgenus Ctclasteb,, Cotteau in Leyinerie et Cotteau (genus), 

 1856, Cat. Eel. Foss. de Tyrm. p. 27 {Extr. Bull. Soc. Geol. de 

 Fr. ser. 2, vol. xiii.) ; 1863, Ech. Foss. des Pyren., Cony. Set. de 

 France, 28 Sept. vol. iii. p. 57; 1887, Pal. Fr., Terr. 

 Eocene, p. 447, pi. 123, and Bull. Soc. Zool. de Fr. vol. xii. 

 pp. 564 & 632. 

 Anterior groove slight abactinally, lost at the ambitus. Antero- 

 lateral ambulacra divergent. 



Apical system with three or four genital pores, and a central 

 madreporite separating the posterior basal plates. Peripetalous 

 fasciole subcircular, often more or less deficient; a subanal fasciole. 

 Fossil. Eocene : Europe, N. Africa ? 



Genus Beissopatagtjs, Cotteau, 1863, Ech. Foss. de Pyren. 



p. 143. Dames, 1877, Palceontoy. Bd. xxv. p. 82, pi. xi. fig. 2. 



Duncan Sf Sladen, 1884, Pal. Ind. ser. xiv., Foss. Fch. W. 



Sind, p. 226. {Amended.) 

 Test of medium size, oval, moderately tumid abactinally, lower 

 and subcarinate posteriorly, flat actinally, anterior groove mode- 

 rate at the ambitus, but small abactinally ; broad depressed areas 

 around and including the petaloid parts of the lateral ambulacra ; 

 a definite interradial ridge separating the lateral petals. 



Apical system excentric in front. Anterior ambulacrum with 

 small pores and in a slight depression ; anterior pair short, widely 

 divergent, much curved, concavity forwards, not closing ; pores 



