118 THE FOSSIL ECHINOIDEA 



Test circular in marginal contour, considerably depressed, the diameter being about 

 twice and a half the height, regularly convex above, sloping down to a rather thin 

 margin or side, which is rounded and only slightly tumid. 



Ambulacral areas less than one half the breadth of the interambulacral areas. Pori- 

 ferous zones very flexuous at the ambitus, where there are six or seven poriferous plates 

 to each whole or compound ambulacral plate, and the pairs of pores are arranged in a 

 vertical semicircular arc. Towards the apical portion of the area the poriferous zones 

 become straighter, and the pairs of pores stand in almost simple rectilineal series. The 

 ambulacral plates bear one large primary tubercle and a few widely spaced, uniform, 

 but irregularly disposed granules on the inner portion of the plate, and also a few on 

 the aboral margin of the plate. 



The interambulacral plates are wide, with one large primary tubercle, equal in size 

 to those of the ambulacra, placed exactly in their midst, and surrounded, except on the 

 adoral side, by a more or less indistinct circlet of granules. There is one small 

 secondary tubercle midway between the primary and the poriferous zone, and two or 

 three small, scattered miliaries. The inner portion of the plate is occupied only by a 

 few uniform and very widely spaced granules, which are quite irregular in their arrange- 

 ment, the general paucity of granules giving a very naked appearance to the plate. The 

 primary tubercles are crenulate and imperforate, the ambulacral series being equal in 

 size to the interambulacral. 



Bemarks. In profile view and in many of the points of detail this form would seem 

 to present some superficial affinities to the Echinoid named Echinometra, Thomsoni by 

 d'Archiac and Haime *. It differs, however, in several of the most essential particulars 

 recited by those authors in their description ; and it would obviously be impossible to 

 draw a just comparison between the fragmentary material at our disposal and the 

 species in question, without a direct comparison with the type ; respecting the generic 

 association of which we may here remark that we feel much hesitation in accepting the 

 determination of our learned predecessors. The type of Echinometra Thomsoni, d'A. & 

 H., is not to be found in the collection at the Geological Society in London. There is, 

 however, a specimen which corresponds with the fig. 13a {loc. cit.) and which bears a 

 ticket in the handwriting of M. J. Haime inscribed " Echinometra Forbesi, J. Haime." 

 This specimen is in a much better state of preservation than the Sindian fossil under 

 notice, and we consider it to be a different species. The arcs of pores are more curved, 

 and the curvature is maintained up to the apex, whereas in our form the poriferous 

 zones become straight. The secondary tuberculation is much more developed, and 

 there is much difference in the contour and general facies. Furthermore, M. Haime's 

 type is in a red matrix, resembling that of the Eanikot series, whilst the present fossil 

 is from the true Nummulitic Limestone. Carefully weighing the foregoing considera- 

 tions, we feel justified in regarding the Khirthar specimen as an independent species. 

 It is much to be desired that more perfect material will be forthcoming, in order that 

 the description may be completed. 



* An. foss. de I'lnde, p. 207, pi. xiii, figs. 13a, 135. 



