OF WESTERN SIND. 131 



The peristome is slightly excentric in front; unfortunately the surrounding 

 portions of the test are obscured in the specimens at our disposal. The structure of 

 one of the posterior ambulacral areas is well preserved between the peristome and the 

 margin ; near the peristome there is a tendency to form a double row of pores — an 

 appearance arising not so much from additional pores as from an alternate disposition 

 of the normal pores through a slight alteration of their position on the plate ; a few 

 additional small intercalated plates, however, are present here and there. Near the 

 margin the arrangement of the ambulacral plates recalls that found in Amhlypygus — 

 namely, one very small triangular intercalated plate inserted between two large ones at 

 their outer margin, thus forming a triplet, which is succeeded by similar triplets, the 

 small intercalated plates being consequently every third plate. Nearer the peristome, 

 in the form under notice, the small intercalated plate is found between nearly every 

 other large plate, and sometimes two intercalated plates may occur together. 



The periproct is preserved in only one example. It is large, elongately oval, and 

 narrow, with the greatest diameter corresponding with the longitudinal axis of the test ; 

 it is placed entirely on the flat actinal surface and comes up close to the margin. The 

 major and minor diameters of the aperture measure 12 millim. and 6-5 millim. 

 respectively. 



BemarJcs. Although only fragmentary specimens of this species have been found, 

 the form is well marked by the peculiar helmet-shaped outline of the test, by the 

 character of the ambulacra, as well as by the character of the ornamentation. In none 

 of the other Indian species are the primary tubercles so widely spaced. 



Dimensions. The following measures are only approximate, as no entirely perfect 

 specimen is contained in the collection : — 



Length of the test . . . 

 Breadth of the test . . . 

 Height of the test . . . 



Another specimen is too much damaged to permit of any measurements. 

 Localities. In the Khirthar series : — i. Dharan Pass (east side), near Laki. Survey- 

 number ^. 



66 



ii. Phitto, west side of the Dharan range. Survey-number ^^■ 



Illustrations of the Species in Plate XXIV. 

 Fig. 5. Abactinal view of a fragmentary test : natural size. 



6. Longitudinal profile of the same specimen : natural size. 



7. Longitudinal profile of another test : natural size. 



8. A portion of an ambulacral petal at its widest part : magnified. (Same 



test as Figs. 5 and 6.) 



9. Terminal extremity of the same petal : magnified. 



10. Portion of an ambulacral area on the actinal surface, showing the arrange- 

 ment of the ambulacral plates near the peristome : magnified. 



