212 THE FOSSIL ECHINOIDEA 



The apical disk is excentric in front, its distance from the anterior margin being 

 about three eighths of the longitudinal diameter of the test. The four generative pores 

 are very closely placed, the posterior pair being slightly wider apart than the anterior 

 pair. The five ocular pores are remarkable for their large size, being quite equal to 

 the generative pores. The pore corresponding to the odd anterior ambulacrum is 

 placed in front of the anterior pair of generative pores, forming with them a triangle. 

 The posterior pair of ocular pores are very wide apart, being separated by the extensive 

 prolongation of the central madreporiform body; and the position of each of these 

 pores is in a line with the two generative pores on its own side of the median line and 

 the odd anterior ocular pore ; there being thus two converging lines of four pores, 

 counting the odd anterior pore twice. The lateral pair of ocular pores are external to 

 the anterior pair of generative pores. . 



The groove of the odd anterior ambulacrum is very shallow and feebly defined. 

 The poriferous zones are straight, with the pores very minute and the pairs compara- 

 tively closely placed. 



The petaloid ambulacra are comparatively short and are sunken in deep grooves, 

 the margins of which are rounded or bevelled, as it were, on to the general area of the 

 interradia. The anterior pair are slightly longer than the posterior pair ; they proceed 

 in a straight line from the apex towards the margin, are very widely divergent, and 

 subtend an angle of about 130°. The posterior petals inclose an angle of about 52°, 

 are rather shorter than the anterior, and their course is straight from the apex towards 

 the margin. Th6 poriferous zones of the petaloid ambulacra are wide, straight, and 

 equal, with pores transversely oval, wide apart, and united by a well-deiined conjugating 

 groove, adjacent pairs and grooves being separated by narrow costse bearing a series of 

 small ill-defined granules. The poriferous zones diminish slightly in breadth at the 

 extremities, but in the case of the anterior zones of the anterior pair of petals the 

 decrease in size at the apical extremity is considerable and rapid, seven or eight pairs 

 being almost entirely aborted. Furthermore, a few pairs are aborted in all the zones 

 at the apical extremity, which gives a singular and disconnected appearance to the 

 apical disk. The interporiferous areas are narrow, and their width is less than the 

 distance of the pores apart. 



The peristome is large and more excentric in front than the apical disk, but 

 unfortunately the neighbouring portions of the test are destroyed and no further obser- 

 vations are possible. 



The periproct is large, subcircular, and placed at the extreme summit of the 

 posterior extremity, the diameter of the aperture being nearly equal to half the appa- 

 rent depth. At the sides of the aperture the test is more coarsely tuberculated than 

 the general surface of the interradia ; and beneath the periproct, where a slight depres- 

 sion occurs, there is some coarse and widely spaced tuberculation also. 



Two fascioles are present — peripetalous and subanal. The peripetalous fasciole is 

 only slightly sinuous in the lateral interradia, where a sharp, short, double bend at 

 right angles takes place near the middle of the anterior column of plates of the inter- 

 radium. Within the boundary of the fasciole some large isolated tubercles are present 



