192 THE FOSSIL ECHINOIDEA 



belonging to the posterior zone of the posterior petals are included within the fasciole, 

 and mark its lateral boundaries. 



The presence of a peripetalous fasciole is very doubtful. In none of the specimens 

 is the delicate ornamentation of the test within the region of the petals sufficiently well 

 preserved to enable this point to be settled. In one of the specimens which has some 

 portions fairly well preserved an arrangement of granulation may be observed at the 

 extremity of the antero-lateral petal, and extending for a short distance close along the 

 posterior margin of the groove, which is rather suggestive of a fasciole. There is also a 

 slight tumidity on one of the plates about midway on the anterior margin of the posterior 

 petal, which might possibly indicate the line of direction taken by the supposed fasciole 

 in crossing the postero-lateral interradium; but no actual band is discernible. The 

 strip of granulation above referred to is, however, somewhat ill-defined, and wanting in 

 compactness — a fact which, together with the inability of finding any trace of the fasciole- 

 structure elsewhere, leads us to entertain very gl-eat doubts as to the presence of a 

 second fasciole in the Spatangoid under notice. 



Bemarks. This very interesting form is readily distinguishable either from its con- 

 geners or any species with which we are acquainted. At first sight it strongly suggests 

 the outline of Towaster, but the structure is altogether different. The very doubtful 

 presence of a peripetalous fasciole, which has been remarked upon above, is the only 

 point upon which we hesitate in referring this Spatangoid to the genus Micraster. Until 

 more perfectly preserved specimens are received, we do not feel justified in taking any 

 other course. 



Dimensions. 



millim. 

 Length of the test 36 



Breadth of the test 34-5 



Height of the test 27-5 



Length of the antero-lateral petals 12-5 



Length of the postero-lateral petals . . . . 11 



Breadth of the paired petals 4-3 



Breadth of the odd anterior petal 2-75 



Transverse diameter of the peristome .... 4-5 



Longitudinal diameter of the peristome . . . 2"25 



Locality. In the Khirthar series of strata: Baili, west of Tong. Survey- 

 number -gg^. 



Illustrations of the Species in Plate XXXVII. 



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. 



4. Odd anterior ambulacrum : magnified. 



5. Portion of one of the petaloid ambulacra: magnified. 



6. Apical disk : magnified. 



