GENERA AND GROUPS OP TUE ECHINOIDEA. 235 



the actinal plastron. Fascioles : a peripetalous, and usually 

 a lateral, which diverges from the former near the ends of the 

 antero-lateral petals and passes beneath the periproct. 



Fossil. Tertiary : England, Europe, India, Australia, West 

 Indies, N. America, N. Africa. 



Recent. N.E. Atlantic coast, Florida, West Indies, S. America, 

 Cape of Grood Hope, Mediterranean, Eed Sea, Indian Islands, 

 -Japan, Philippines, China, Arafura Sea, Eiji, Marion aud Ker- 

 guelen Islands (37-1507 fms.). 



The synonymy of this genus is given by A. Agassiz in his 

 ' lievision.' Unfortunately S. giblerulus has been placed in 

 Agassizia by M. Cotteau, and subsequently in Anisaster, Pomel. 

 Apparently the genus Faraster, Pomel, is a synonym. 



Grenus Prenaster, Desor, 1853, Note sur les Ech., Act. de la 

 Soc. Selv. d. Sci. Nat. p. 279 ; 1858, Synopsis, p. 401. 

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

 pt, ii, p. 90, pi. xix. 



Test small or moderate in size, ovoid in marginal outline, 

 rounded in front and truncated posteriorly, tumid and depressed 

 dorsally, but rather boldly arched, convex behind the peristome 

 actinally. There is no anterior groove. 



Apical system very excentric in front, small, with four perfo- 

 rated basal plates, and the madreporite passing backwards and 

 separating the posterior basal and radial plates. 



Ambulacra diver.-^e, the anterior flush, with pairs of small 

 oblique pores ; the paired ambulacra in very faint groove^i, not 

 closing, subpetaloid, ahnost straight ; the anterior the longest and 

 very divergent ; some slight difference may exist between the 

 dimensions of the anterior and posterior rows of pairs of pores in 

 the antero-lateral ambulacra. 



Peristome excentric iu front, with a strong labrum. Periproct 

 at the top of the posterior truncation. 



Tubercles small to moderate, scrobiculate, perforate and crenu- 

 late, largest actinally. 



A peripetalous fasciole wanting anteriorly, not extending 

 beyond the point of junction with the marginal fasciole. A 

 marginal fasciole surrounding the test, dipping down in front, and 

 passing below the periproct behind. 



Fossil. Eocene : Europe, Asia (W. Siud), N. Africa. 



