48 THE FOSSIL ECHINOIDEA 



In the interporiferous areas on the actinal surface there is a straight vertical series 

 of primary tubercles, crenulate and imperforate, placed on each margin, and here and 

 there a companion tubercle of similar size placed on the inner part of the plate ; 

 ordinarily, however, this part of the plate is occupied only with a few small and widely 

 spread miliaries. It is impossible to state accurately the disposition of the tubercles 

 above the ambitus. 



The plates of the interambulacral area are very broad and short ; in the actinal 

 portion there are two continuous vertical series of primary tubercles, placed rather 

 nearer to the poriferous zone than the middle of their respective plate. Near the 

 ambitus there may be one or even two similar tubercles on either side of the central 

 primary, standing in a horizontal line, the number of tubercles decreasing towards the 

 peristome. 



The ornamentation of the abactinal portion of the area is undistinguishable ; but it 

 is probable that the inner half of the plate was occupied only by rather widely spaced 

 miliary granulation. The primary tubercles of both areas are small and uniform in 

 size. 



Peristome small and more or less sunken, with narrow and deeply-indented 

 mouth-slits. 



1. .^OLOPNEUSTES DE LoEiOLi, sp. nov. Plate VIII, Figs. 6-9. 



The test is thin, pentagonal in marginal outline, tumid at the ambitus, and slopes 

 thence gradually to a narrow apex. The actinal surface is generally flat, but there is 

 a slight convexity about it, and the moderately sized peristome is decidedly sunken. 



The breadth of the test is nearly double the height; the ambulacra are slightly 

 more prominent above the ambitus than the interradial areas, which have a strongly 

 marked median depression ; and the primary tubercles are small and equal throughout, 

 few in number, imperforate and crenulate. 



The pores are in simple series near the peristome, but increase in number in relation 

 to the interradial plates, towards the ambitus, and on the upper part of the test, where 

 they are in several series of arcs in a broad zone. 



The apical system is wanting in the specimen. 



The ambulacra are broad, more than one half the width of the interradial areas just 

 above the ambitus, and then contract gradually towards the peristome. The poriferous 

 zones are wide, being, above the ambitus, equal to or even more than half the breadth of 

 the interporiferous area, narrowing greatly towards the peristome. The pores on the 

 abactinal portion of the zone are arranged in almost horizontal arcs of five or six pairs, 

 very regular and very closely placed. Just below the ambitus on the actinal surface the 

 number of pores in each arc is six, and the angle of obliquity about 45° ; rather nearer the 

 peristome the number is reduced to five ; and about midway between the ambitus and 

 the peristome there are only four, and these are arranged in slightly oblique lines 

 instead of arcs ; the number is then reduced to three, and the obliquity becomes still 

 less, until close to the peristome the pairs of pores stand in almost straight and 



