32 THE FOSSIL ECHINQIDEA 



1. Cyphosoma abnoemale, Duncan 8f Sladen, sp. nov. Plate VII, Figs. 1-7. 



The test is depressed, circular in marginal outline, very bulging at the sides, nearly 

 flat at the abactinal surface, and slightly concave actinally, notwithstanding some 

 convexity of the areas around the rather small sunken peristome. 



The apical system is small ; details not preserved. 



The ambulacra are comparatively narrow, and enlarge moderately only, at the 

 ambitus ; they are not quite one half of the breadth of the interradial areas at the 

 most convex part of the test, and the broad poriferous zones are on a slightly lower 

 level than the inter poriferous areas. 



The pores are very small and numerous, bigeminal, and more or less in arcs from 

 the ambitus to the apical system, and in slightly arched simple series near the peristome. 



At the ambitus the ambulacral tubercles are larger than elsewhere, and they 

 diminish in size more suddenly towards the peristome than towards the apex, and they 

 are less numerous in the former direction. The larger tubercles have a broad circular 

 base ; the boss slopes gradually upwards to a well-developed neck, which is surmounted 

 by a small mamelon, rather flattened at the summit and imperforate. The crenulation 

 is distinct. A scrobicular circle of a few large and small miliaries is around each 

 tubercle ; and near the poriferous zone the larger of these miliaries are in relation to 

 a poriferous plate, a line of depression intervening between the successive miliaries. 

 A small secondary tubercle is seen, here and there, at the ambitus, and usually they 

 are placed, solitarily, between the vertical series of larger tubercles. Near the apex the 

 tubercles are small, and the circle of smaller tubercles is ill-defined ; but there are a 

 few tubercles of intermediate size in vertical series. Still nearer the ambitus the 

 tubercles are larger, and begin to assume the character of those at the ambitus. Near 

 the peristome there is a short close vertical series of small tubercles of intermediate 

 size, followed by wider-apart ones, which gradually become typical tubercles. In the 

 close series the scrobicular circle of miliaries is not seen ; but it commences directly 

 there is any appreciable distance between the tubercles. 



The interradial areas are wide, even at the apex ; and their tubercles are small 

 away from, and large and projecting at the ambitus ; they are larger than those of 

 the ambulacra. A large tubercle at the ambitus, has a broad base, a slanting conical 

 boss, which is broadly crenulate, with a large and narrow neck and a small, rather 

 flat mamelon. The scrobicular circle, of a single row of large miliaries, is incomplete 

 between the vertical series of tubercles, but nearer the apical system it is nearly com- 

 plete. There, the tubercles are wider apart, and the miliary circle is sparsely furnished. 

 At the actinal surface the tubercles are larger than at the apex, and the scrobicules of 

 the vertical series are not separated. 



The median area of the interradials is wide and very sparely ornamented with large 

 and small miliaries near the apex, a very few small tubercles with crenulated bosses 

 being placed in alternate vertical series near the median line of suture. They are 

 largest at the ambitus. 



Between this series and the scrobicular circles are large miliaries, many with a 



