80 THE TEETIAKY FOSSIL ECHINOIDEA 



round the edge ; and the greater part is occupied by the madreporic body, which is 

 covered with nodular granules. There are four generative pores, which are large, and 

 the anterior pair are closer than the posterior. The ocular plates are very small. 



The ambulacra are unequal, moderately broad, the posterior being the longest 

 and the others subequal ; the odd ambulacrum is slightly narrower and shorter than the 

 others, and all pass far towards the margin, but none of the petaloid parts reach it. 

 The odd ambulacrum is widely open at its marginal end, but still the poriferous 

 zones converge there slightly ; the antero-lateral tend to close, but do not, and this 

 is observed in a less degree in the postero-lateral ambulacra. The interporiferous 

 zones are broad, slightly convex, and raised above the level of the rather sunken pori- 

 ferous zones. The posterior ambulacra have the broadest interporiferous zone, and all 

 are ornamented with a close small tuberculation in small sunken scrobicules, the 

 intervening part being finely, sparely, and distinctly granular. The tubercles are 

 barely above the test, and have small mamelons. 



The poriferous zones are broad, the pairs are obliquely placed, and the pores are 

 large and conjugate. The pairs are separated by well-developed granular costse. The 

 pores of the outer row are elongate-comma shaped, and the inner pores are nearly circular. 



The poriferous zones of the anterior odd ambulacrum, slightly petaloid in their 

 contour near the apex, diverge gradually to their ends ; the inner lines of pores are 

 nearly in straight series, and the outer form curves on account of the breadth of the 

 poriferous zones increasing gradually to one half of their length and then diminishing 

 to a point. 



The antero-lateral ambulacra form a widely open angle of 170°; are at first narrow 

 and petaloid, then are enlarged in breadth, and they become gradually narrower to their 

 end above the margin. The anterior poriferous zone is the shortest, and is nearly straight 

 in its direction from the apex to some distance from the margin ; and the posterior 

 zone is decidedly curved, with the convexity posterior. Towards the end of the 

 posterior zone the pairs of pores diminish in breadth and turn slightly backwards. 



The interporiferous zone of the posterior ambulacra is wider than that of the other 

 ambulacra; and the poriferous zones are slightly unequal, the anterior being the 

 longest. The anterior zone is more curved than the posterior, which is nearly straight 

 in comparison, and there is a tendency to close. 



The interradia are large, the anterior are singularly flat abactinally, and the 

 posterior one has no unusual convexity. The ambulacra are continued over the margin 

 in single series ; and there is a phyllode in a narrowing groove corresponding with 

 each one. 



The pores are doubled near the peristome ; they are in depressions which resemble 

 scrobicules without tubercles. 



The ornamentation of the abactinal part of the test generally resembles that of the 

 interporiferous zones; it becomes closer and smaller at the margins, and increases in 

 size and is wider apart and largest near the peristome. It is especially large on the 

 bourrelets, a little way off the peristome. 



