150 THE FOSSIL ECHINOIDEA 



Sulfamily ECHINOLAMPINM. 



Genus EOLAMPAS, Duncan & Sladen, 1882. 



(See anted,, p. 61, Part ii.) 



1. EoLAMPAS BXCENTEicus, Buncan & Sladen. Plate XXXI, Figs. 11-15. 



Test of small or medium size. Marginal contour an oval escutcheon-shape, rounded 

 in front, expanding gradually up to the point of greatest breadth, which is situated on 

 a line with the outer extremities of the posterior petals, and from thence the outline 

 contracts rapidly to form the rather prominent posterior rostration. The greatest 

 breadth is about five sixths of the length, or as 0-83 : 1 ; the test, however, having a 

 more elongate appearance than those figures would seem to indicate, consequent on the 

 peculiarity of shape. The dorsal surface is subdepressed, generally convex, forming a 

 subconoidal peak at the apical summit, and a more or less definite trace of carination 

 along the median line of the posterior interradium. The actinal surface is almost flat, 

 very faintly depressed in the region of the peristome, and merging outwardly into the 

 rounding of the margin. The margin is well-rounded, moderately thick and tumid. 

 Seen in longitudinal profile the extreme excentricity of the apical summit is remarkable, 

 causing the anterior slope or curve to be rapid and precipitous, whilst the posterior 

 slope is a gentle and gradual incline, until the posterior rostration is reached, over 

 which it bends with a rapid well-rounded curve, terminating vertically. Seen in trans- 

 verse profile the dorsal outline is markedly subcorneal. 



The apical disk is small and very excentric in front, its distance from the anterior 

 extremity being three tenths of the length of the test. There are four generative pores, 

 the anterior pair being much closer together than the posterior pair ; and five ocular 

 pores, which are small and inconspicuous, excepting the odd anterior one, which appears 

 to be larger and more deeply sunken than the rest. 



There are only four ambulacral petals, the odd anterior ambulacrum being aborted. 

 In the place of the pairs of pores of the odd anterior ambulacrum slight grooves are 

 to be seen amongst the ornamentation, which are much more numerous than the pairs 

 of pores in the other ambulacra ; and occasionally in small specimens there is the 

 indication of a very minute single pore here and there, but in large examples even 

 these appear to be aborted. The paired petals are long and narrow, slightly converging 

 towards the outer extremity, and the anterior pair are rather shorter than the posterior 

 pair. The poriferous zones are equal, comparatively broad, and more than half the 

 width of the interporiferous area. The pores are very small, round, wide apart, and 

 are united by a well-defined conjugating furrow, the direction of which is oblique, in 

 relation to the median line of the petal. The furrows are separated by rather broad 

 costee, ornamented with a single line of 5 or 6 small uniform-sized granules. The inter- 

 poriferous areas are flush with the surface of the test, and their ornamentation is 

 similar to that of the interambulacral areas of the test. The petals in their direction 

 are nearly straight, the anterior pair being widely divergent and enclose a large angle, 

 whilst that enclosed by the posterior pair is small. 



The peristome is small, transversely, oval, slightly angular laterally, and its position 



