90 THE FOSSIL ECHINOIDEA 



jS. d' TIrhani (Forbes), of the Barton series of Alum Bay. It has considerable affinities 

 with S. africanus, de Loriol, from the Nummulitic of Egypt. But the whole of the 

 test not being accessible, it is impossible to do otherwise than state that the form 

 belongs to the Schizasters with deep and keeled anterior grooves, deep and sinuous 

 antero-lateral ambulacra, and small posterior petals and only two generative pores. There 

 is a ScMzaster from Kach which is allied to this form ; but there are specific distinc- 

 tions. But as it is probable that the Ranikot species had only two generative pores, we 

 reproduce, with considerable hesitation, however, the details of the form from Kach. 



Genus PRENASTEE, Desor, 1853. 



Test tumid, ovoid, regularly founded in front, truncate behind. 



Apical system very eccentric in front. 



Ambulacra subpetaloid, narrow, almost straight ; the anterior pair widely divergent, 

 almost transverse, placed in. very faint grooves, open at the extremities. The odd 

 ambulacrum is scarcely visible, and nearly flush with the surface of the test, there being 

 no anterior goove. 



Peristome bilabiate, inferior lip prominent. 



Periproct oval, at the summit of the posterior extremity. 



Two fascioles, a peripetalous and a marginal. The peripetalous fasciole is incom- 

 plete and wanting in front, not extending beyond the point of junction with the mar- 

 ginal fasciole. This latter completely surrounds the test, dipping far down in front 

 (sometimes so much as to appear on the actinal surface), and passing posteriorly below 

 the periproct. 



Tubercles are small and inconspicuous, perforate, crenulate, sunken in scro- 

 bicules. 



1. Peenaster ovifoemis, sp. nov. Plate XIX, Figs. 1-6. 



The test is subovoid, long, tumid, rounded in front, at the sides, and above, and 

 truncated behind. It is longer than broad and broader than high, and is highest cen- 

 trally, and the slope is sharpest anteriorly. Below, the surface is convex. 



The apical system is eccentric in front, and the peristome also. The periproct is 

 close to the top of the posterior truncation, which merges superiorly into a projecting 

 point. 



The apical system is small ; and there are four generative pores, tlie posterior pair 

 being rather the widest apart. The madreporic disk, in connexion with the right ante- 

 rior plate, passes backwards, separating the posterior lateral generative plates, also sepa- 

 rating the ocular plates of the posterior lateral ambulacra in a very slight degree. 



The ocular pores are small but distinct, and are at the bottom of minute hollows 

 in their plates. 



There is no anterior groove ; and the very minute series of pores of the odd ambu- 



