136 THE FOSSIL ECHINOIDEA 



marked and distinctive that we feel obliged to regard it as an independent species. No 

 other Clypeastroids were obtained from the same locality. 



The size of the specimen is large for the genus ; the marginal contour of the test 

 is almost circular, slightly protruding posteriorly. The longitudinal profile is almost 

 regularly convex, but slightly more tumid anteriorly than posteriorly ; the transverse 

 profile is regularly convex, with no tendency to a subconical form, and the height of 

 the.test is not great. The margin is well and evenly rounded, passing over impercep- 

 tibly to the actinal surface, which is somewhat flattened ; and there is scarcely any 

 impression around the peristome. 



The. apical disk is small and central; and the four genital pores are large and 

 occupy nearly the whole of the genital plates. The anterior pair of plates are placed 

 close together ; and the madreporic puncture, instead of being situate between them 

 as in the preceding species, is pushed forward towards the middle of the system. 

 The ocular plates are exceedingly minute, and fit in at the outer portion of the 

 juncture of the genital plates. The posterior pair of genital plates are wider apart than 

 the anterior pair, and their distance apart is greater than that separating an anterior 

 from a posterior pore on the same side. 



The ambulacral petals are comparatively long and rather more developed in 

 character than usual in Hchinocyamus. The poriferous zones are straight and diverge 

 as they proceed outward ; this character is most marked in the odd anterior ambula- 

 crum, which is much wider than the paired petals. In this petal the interporiferous 

 area is three, or even more, times the width of the poriferous zone and wedge-shaped 

 in outline ; but in the paired petals the interporiferous area is only a little wider than 

 the poriferous zone. The interporiferous area is perfectly flush with the level of the 

 test, and there is no tendency to form a keel. The pores are equal or subequal, and 

 faintly elliptical and placed oblique, and the pores of a pair are almost equidistant 

 throughout the ray, and there is no trace of conjugation whatever between the pores. 

 There are ten or eleven pairs of pores in the odd anterior petal, and nine or ten in the 

 paired petals, with one or two single pores in each. 



The peristome is pentagonal and very slightly excentric posteriorly, only a shade 

 removed from the subcentral position. The periproct is small and elongately oval, 

 rather nearer to the peristome than the posterior margin. No further details respecting 

 these structures can be made out, in consequence of the manner in which the test is 

 preserved. 



The tuberculation of the test is minute and uniform. The primary tubercles 



are sunken in scrobicules, and more numerous and crowded than in the preceding 



species; and the interspaces are consequently smaller and more homogeneous in 



character. -^ . 



Dimensions. ^^^-^ 



Length of the test 9 



Breadth of the test 8-75 



Height of the test 5 



Locality. In the Khirthar series of strata. North by east of Meting. Survey 



number -gg-. 



