186 THE FOSSIL ECHINOIDEA 



phyllode is rather shorter than those of the lateral ambulacra ; and a pitted structure 

 occurs along the actinal course of the odd anterior ambulacral area, instead of 

 scrobicules with tubercles as in all the others. These pits extend nearly to the margin, 

 and are smaller and wider apart than in the posterior interradial pitted space mentioned 

 above. 



The periproct is above the ambitus, and somewhat away from the margin ; the 

 aperture is large, transverse, and overhung by the conspicuous rounded supra-anal pro- 

 jection of the dorsal posterior interradial carination. The portion of the test beneath 

 the periproct is slightly hollowed into a wide but shallow groove, which extends to the 

 rounded margin, and, passing over it, becomes fainter, but still feebly indents the con- 

 tour of the posterior truncation. 



Young form. A small test, 20 millim. in length, presents all the characteristics of 

 the adult, the specific fades being unmistakable. 



Variations. A considerable amount of variation within small limits is exhibited by 

 the series of Khirthar specimens. This principally affects : — (1) the marginal contour, 

 by the narrowing of the anterior portion of the test ; (2) the dorsal area, by varying 

 degrees of tumidity ; and (3) the actinal area, by an increase or a diminution in the 

 amount and distinctness of the longitudinal concavity, together with a greater or less 

 tumidity of the margins. 



A singular monstrosity occurs in one of the specimens, which consists in having the 

 odd anterior petal entirely aborted. Notwithstanding this extraordinary defect, the 

 shape of the test maintains its regularity, and the missing ambulacrum is only noticeable 

 on examination. Only three genital pores are present, and only the posterior pair 

 are in their proper position. The specimen is figured on account of this interesting 

 malformation. 



Dimensions. 



a b. c. d. e. f. 



millim. millim. millim. millim. miUim. millim. 



Length of the test ... 34 35 42 37 36 20 



Breadth of the test . . 26 26 30-5 27 27-5 15 



Height of the test . . . 19 18 16-5 20-5 18 10 



Width of odd anterior ambulacrum of specimen marked " a" . 4 millim. 

 Width of interporiferous area of the same petal 1"8 „ 



number ™ 



Localities. In the Khirthar series: — i. Twelve miles east of Kandaira. Survey- 



Der ^^. 



ii. Aongar hiU-scarp, east of Meting Eailway-station. Survey-number 5^. 



Illustrations of the Species in Plate XXXIII. 



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



2. Longitudinal view of the same test : natural size. 



3. The same test, seen from behind : natural size. 



