38 THE TEETIARY FOSSIL ECHINOIDEA 



height behind the apical system is not so great as that of the type, although the whole 

 height there of the test may be equal to that of the type. 



1. ScHizASTBR Baluchistanensis, d'ArcUttc, variety. Plate V, figs. 5-8. 



The test is tumid, elongate, longer than broad and broader than high ; the margin 

 as seen from above is rounded in front with a very faint anterior groove, slightly 

 flattened on either side on a line with the terminations of the antero-lateral ambulacra, 

 and more convex and widest a little further back on a line anterior to the apical 

 system. From this point the test is curved sharply backwards, becoming narrower and 

 almost pointed at the median line posteriorly. 



Seen from below, the margin has the same contour as in the view from above, 

 except posteriorly, where there is a slight truncation instead of a pointed end ; and the 

 truncated part is overhung (in the natural position) by the pointed end of the upper 

 surface, the periproct immediately beneath this being visible from below. The test is 

 tumid all round the margin except posteriorly, where it is truncated, and its highest 

 point is in front of the posteriorly excentric apical system, on the keels which bound 

 the anterior ambulacrum. Omitting these keels, the highest point will be the apical 

 system, and the top of the test is continued backwards over a slight depression on to a 

 keel in the median line. This slopes backwards and downwards posteriorly, and ends 

 by overhanging the periproct. In front of the apex the test slopes very gradually along 

 the line of the anterior ambulacrum, forming a gentle curve down to the tumid margin. 

 On either side of the ambulacrum is a keel which is high slightly in front of the apical 

 system, and which slopes in front and merges into the general surface before reaching 

 the margin. The view from the front shows the groove for the anterior ambulacrum, 

 the high keels diminishing forwards, the groove slightly diminishing to the peristome. 

 Posteriorly the test is oblique from above downwards and forwards, slightly concave in 

 the vertical line, and the lowest point there is the projection at the end of the plastron. 

 Actinally the test is convex from side to side, flattened in the middle over the plastron, 

 but still slightly convex there, and it rests on the plastron near the centre. The 

 position of the peristome is far in advance of the centre, and its lower lip is slightly 

 prominent. Finally, the plastron is slightly convex from before backwards. 



The apical system is small ; there are four generative pores, of which the two anterior 

 are very small and wide apart ; and the posterior are very large and wider apart than 

 the anterior, to which they are very close. The ocular pores are small, and the anterior 

 is between the anterior generative pores, whilst the antero-lateral ocular pores are on a 

 line with the first pair of generative and the anterior ocular pores. The posterior 

 generative pores are upon a narrow slightly raised keel, which passes transversely from 

 one antero-lateral interradium to the other ; and the anterior are in a depression in 

 front of it and behind a rapid backward slope of the two anterior keels. 



The anterior ambulacrum is in a decided narrow and rather deep groove, bounded 

 by a high keel on either side except in front. Near the apical system the groove has 

 a flat floor, which becomes concave further out, and the margins of the floor are slightly 



