146 THE FOSSIL ECHINOIDEA 



the actinal area, the comparatively thin and angular margin, and the well and uniformly 

 arched dorsal surface ; it is further characterized by the curve of the posterior petals, 

 the subrostrate form of the posterior extremity, and perhaps also by the smaller and 

 scantier primary tuberculation. When compared v?ith a specimen of A. suhrotundus 

 of precisely similar size, these differences are very striking ; they also appear to be 

 sufficient to distinguish the species from the other known members of the genus. 



Dimensions of type specimen. 



miUim. 



Length of the test 60 



Breadth of the test 55 



Height of the test 20 



Greatest width of the poriferous zone 2*25 



Width of the interporiferous area at the above place 4 



„ „ „ at the margin . . 5-5 



Greatest width of the postero-lateral petal .... 8-75 



„ „ anterior petals 8 



The proportion of length to breadth = 1 : 0'916. 



The proportion of length to height = 1:0-333. 



Locality. Khirthar series of strata. Hilly ground south-east of Trak Hill. 

 Survey-number ^||-. 



We also refer to this species a second specimen found at Rois Hill, near Damaj, 

 south of Bula Khan (Khirthar series). Survey-number ^5^. 



Illustrations of the Species in Plate XXVII. 



Fig. 1. Abactinal view of the test : natural size. 



2. Actinal view of the test : natural size. 



3. Longitudinal profile of the test : natural size. 



3. Amblt:ptgus tumidus, Duncan & Sladen. Plate XXVII, Figs. 4-6. 



There is a test of a fine species oi Amblypygus from the Khirthar series, but which 

 unfortunately is so much obscured with matrix and otherwise badly preserved that only 

 a partial description can be given. The test is high, with marginal contour subovoid, 

 the greatest breadth being a little behind the anterior ambulacra, and the curve of the 

 outline being sharper and more contracted posteriorly than anteriorly. The height is 

 greater than half the breadth, and proportional to the length as 052 : 1, and the 

 margins are thick and tumid. The curvature of the anterior slope of the longitudinal 

 profile is less bombous than the posterior ; and the posterior part of the test, as a 

 whole, is thicker (higher) than the anterior. The transvere profile of the test shows a 

 uniform convex curve of fair elevation. The actinal surface has a bombous aspect, and 

 appears to have a very slight central concavity. The ambital margin does not at all 

 overhang, but is bevelled away and well rounded. 



