336 THE FOSSIL ECHINOIDEA 



tinal surface and the contour of the same as seen in longitudinal profile. In some forms 

 the abactinal surface is comparatively depressed and its profile exhibits a more or less 

 uniform and regular convexity, and often even slightly flattened centrally (see Figs, 

 1 and 2). Others, again, have a much greater relative height, and the abactinal surface 

 shows a distinct and conspicuous conoid elevation in the region of the apex, with the 

 anterior slope rapid, and the posterior more gradual and flexuous as seen in profile 

 (compare Figs. 3-5). The breadth of the ambulacral petals is likewise subject to 

 variation, and quite a number of examples with remarkably broad petals, when com- 

 pared with the normal form, may be distinguished ; and furthermore it is of interest to 

 remark that the feature appears generally to be associated with the more or less sub- 

 depressed orbicular forms. An example of this vairiety is represented in Fig. 6, In 

 this specimen the width of the paired ambulacra is ywoq of the length of the test. 



Remarks. This species is closely allied to the form we have nanaed E. Indica, from 

 the Miocene of Kachh. Both are very variable forms, and it would be quite possible 

 to select a series which would appear to form a transition between the two species. 

 Taken as a whole, however, the habit of E. Indica and E. Jacquemonti is different, and 

 immediately strikes the eye. In the former the test is habitually higher, more regu- 

 larly convex abactinaUy, and more tumid laterally. The inequality of the poriferous 

 zones and the amount of their curvature is greater. The excentricity of the apical disk 

 is less, the proportions of the peristomial and periproctal apertures, as well as their 

 form, are different. On these grounds we consider the species distinct, but probably 

 phylogenetically allied. 



Bimensions. 



The largest example in the collection measures 72 millim. in length, and another 

 62 millim. ; but both specimens are too much crushed for the other dimensions to be 

 given with any degree of accuracy. 



Localities. In the Gaj series of strata : — 



i. Scarp of the M61 Plateau, west of Kund (the same scarp as G ^t). Survey- 

 number G -j^. 



ii. Kavine on the south-east of Bill, twelve miles north of Shah-beg (the coral 

 zone). Survey-number G -^3-. 



