316 THE FOSSIL ECHINOIDEA 



Variations. Reference has been made to the variability of the form of the test of 

 this species. The general type may be said to be depressed, with the abactinal surface 

 subconoid, suggesting the habit of the recent Pseudoboletia. Examples of this form 

 bear the Survey-numbers G^j^^ G-^; and a smaller specimen, which perhaps may 

 be classed in the same category, is marked G ^^. A relatively higher and more 

 globular test, of smaller size than the type, is marked G-^Q-^nd G^r', in other 

 respects these examples accord in their structure with the details described above. 

 Fragments of a high test, bearing the Survey-number G -g-g-, are remarkable for pre- 

 senting in conjunction with that character a decided tendency to a subconoid form in 

 the region of the apex, and in having a very distinct depression or wide trough-like 

 encurvature along the median interradial areas on the abactinal surface, causing the 

 test to appear somewhat melon-shaped. The tuberculation was probably less widely 

 spaced than in the type forms of Hippono'e antigua ; but the fragments are unfortu- 

 nately in a very bad state of preservation, and have been long exposed to the action of 

 weathering. With more satisfactory material it may perhaps be found necessary ulti- 

 mately to distinguish this form as a distinct variety, but for the present we abstain 

 from giving it a name. 



RemarJcs. This species is distinguished from H. proavia by the depressed and 

 usually subconoid form of the test, by the narrow ambulacral areas, and by the widely 

 spaced tuberculation of the interradial plates, and the consequently smaller number of 

 tubercles on each plate. 



Dimensions. The greatest diameter of the type specimen measures 127 millim., 

 and the height is about 54 millim. ; but the test has been so greatly crushed that little 

 value can be placed upon the last measurement. A small example, which is only a 

 little crushed, is 82 millim. in diameter and 46 millim. in height ; whilst the frag- 

 ment of another test, which does not appear to have been distorted, represents a test 

 which we estimate at 95 millim. in diameter, and about 47 millim., or probably rather 

 less, in height. A fragment of the high variety with interradial depressions measures 

 65 millim. in height, and belongs to a test rather more than 92 millim. in diameter. 



Localities. In the Gaj series of strata: — 



i. About three miles south-east of Tong. Survey-number G ^^^. 



ii. Scarp of the Mol Plateau, west of Kund (the same scarp as G(\^V). Survey- 

 number G "T^. 



iii. Near the Habb Eiver. Survey-number G -j^. 



iv. Hill-scarp five miles north of Shah Rhiii, on the Naig Nai, south-west of 

 Jhangara. Survey-number G -^j^. 



V. Mol Plateau, fourteen miles north of Shah-beg. Survey-number G -^^ 



Illustrations of the S'pecies in Plate XLIX. 

 Fig. 2. Abactinal view of the test : natural size. 



3. Actinal view of a smaller specimen: natural size. 



4. Profile ^'iew of the same fragment : natural size. 



