152 THE FOSSIL ECHINOIDEA 



Illustration of the Species in Plate XXXI. 



Fig. 11. Abactinal view of the test: natural size. 



12. Actinal view of the test: natural size. 



13. Longitudinal profile of the test: natural size. 



14. Abactinal area, showing the ambulacral petals and apical disk : magnified. 



15. The peristome and surrounding portions of the test: magnified. 



Genus ECHINOLAMPAS, Gray, 1825. 



Test more or less oval in marginal contour, convex above, flat or subconcave 

 beneath, margins more or less tumid. 



Ambulacra petaloid, open at the extremity, and not greatly convergent. Poriferous 

 zones with the inner pores round and the outer pores elongate, the pairs being united 

 by a conjugating groove. Ambulacral summit usually excentric in front. Apical disk 

 compact. 



Peristome subceptral or slightly excentric in front, subpentagonal, transverse; 

 floscelle present, often feebly developed. 



Periproct oval, transverse, inframarginal, or on actinal surface close to the pos- 

 terior margin of the test. 



Ornamentation homogeneous. Tubercles small, perforate, non-crenulate, sunken 

 in scrobicules, uniform and crowded ; miliary granulation more or less compact. 



1. EcHiNOLAMPAS EOTUNDA, Buncan & Sladen. Plate XXVIII, Figs. 1-6. 



Test of moderate size. Marginal contour subcircular, with a slight tendency to 

 elongation in the longitudinal axis, and a slight protuberance, more or less pronounced, 

 in the posterior part of the lateral interradia corresponding with the line of greatest 

 breadth. The length is very little greater than the breadth, the proportion being as 

 1 : 0*94. The dorsal surface is flatly subconoid, the margins being very thick and 

 regularly tumid. The apical summit of the test is excentric in front, and its height is 

 rather more than half the length, being in the proportion of 0*58 : 1. Seen in longitu- 

 dinal profile, the anterior slope of the test is more rapidly inclined than the posterior, 

 and appears to pass continuously from the apex over the thick, high margin as a portion 

 of a parabolic 'curve. The posterior slope is faintly depressed at a short distance from 

 the apex, and is the fullest and most convex just above the posterior margin, over 

 which it passes almost precipitously. The transverse profile shows the subconoid cha- 

 racter of the dorsal surface, and the margins are thick and tumid. The actinal surface 

 is remarkably pulvinate, the test being tumid around the deeply-depressed peristome, 

 the tumidity being greatest along the median line of the posterior interradium, and 

 extending around the lower margin of the periproct. 



The apical disk, which corresponds with the summit of the test, is rather large. 

 There are four generative pores, the anterior pair being closer together than the 

 posterior pair ; and the central disk, which is entirely occupied by the punctures of the 

 madreporite, is large and flat. The ocular plates are small and subcrescentiform. 



