356 THE FOSSIL ECHINOIDEA 



surrounding a triangular space, and merging into the narrow path which is carried over 

 the margin as a series of long plates perforated by one pore. The ornamentation of the 

 actinal surface is of small tubercles, increasing in size towards the mouth and becoming 

 wider apart also ; they are in radiating series and start as it were from certain points on 

 the margin. 



The tubercles, which are small, are upon the usual flat scale-like bases, and are 

 perforate as well as irregularly crenulated. 



Very often the mamelon and part of the top of the boss are deformed. 



In one specimen the odd ambulacrum can be seen fairly well and it is very narrow 

 at the apex, in a very slight groove for a short distance, and the pores are small and 

 environed with granules. Near the apical system there are pairs of pores which soon 

 become placed with one pore well in advance of the other ; nearer the margin there is 

 only one pore to a plate, and this is the rule over the margin. 



The plates of this ambulacrum become larger actinaUy ; but the only double- 

 pored plate is that at the edge of the peristome in the zone " b " plate 1 of ambulacrum 

 III. 



The part surrounded by the subanal fasciole looks backwards and downward, and 

 is heart-shaped. The anus above it is larger elliptical, and is in the posterior narrow 

 and tumid vertical truncation. 



The test when mature is ovoid in outline, but it is truncated posteriorly. It is 

 depressed and there is a general but only moderate slope to the median line of the 

 actinal surface from the rather sharply rounded margin. The highest point is behind 

 the eccentric in front apical system. A younger specimen is proportionally longer in 

 relation to breadth than the more mature forms, and an intermediate specimen is defi- 

 cient in the anterior breadth which is noticed in old forms. Growth seems to take 

 place more decidedly in length and breadth than in height. 



Length of large specimen 9 centim., breadth 78 mm., height 42 mm. 



Length of middle-sized specimen 73 mm., breadth 66 mm., height 37 mm. 



Length of small specimen 44 mm., breadth 35 mm., height 25 mm. 



Localities. Gaj series or Miocene of Sind : Amra Hill, Barri Nai, Pir Gaji, west of 

 Sehwan ; Naig-Nai valley. Survey numbers G ^g^ and G ^^. 



Illustration of the Species in Plate LV- 

 Fig. 9. Actinal view of a medium-sized form. 



The full-sized specimens of this species recall the genus Metalia on account of the 

 comparatively thin margin and shape; but there is no anterior sulcus, the actinal 

 surface is convex, and the abactinal tubercles are not those of the genus. On the con- 

 sideration of the whole of the structures the form appears to be inseparable from the 

 genus Brissus, Klein. 



