236 THE FOSSIL ECHINOIDEA 



situated in slightly excavated scrobicules, which are interspersed with smaller tubercles 

 and with unequal granules. All the tubercles cease near the ambitus, where a peripe- 

 talous fascicle probably existed, but which it has been impossible for us [d'A. & H.'] to 

 verify. The anus is marginal and rather in the upper part ; the periproct suboval and 

 a little longer than wide. The under surface of the body is feebly convex and covered 

 with slightly prominent tubercles, interspersed with small granules, which increase in 

 size from the margin inwards ; the mouth is situated at the anterior third of the major 

 diameter. The single example which we \_d'A. & H.'\ have observed measured 16 millim. 

 in length, and 9 millim. in breadth and height. 



The type above referred to is in the collection of the Geological Society of London ; 

 it is small and much rubbed, and scarcely represents the character of the adult form. 



The large series of examples obtained from the Khirthar strata in Sind enable us 

 to add several observations to the foregoing description. The peripetalous fasciole, 

 whose presence was inferred by d'Archiac and Haime, is always present, but is fre- 

 quently untraceable in badly preserved specimens on account of the extreme narrowness 

 of the band ; it is of wide extent, oval in shape, non-sinuous, encircles the abactinal 

 surface, passing near to the extremities of the ambulacral petals, and consequently not 

 far above the ambitus ; in fact, anteriorly, it is actually coincident with the ambitus. 

 In addition to the peripetalous fasciole there is a remarkably well-defined subanal 

 fssciole, of which no mention is made by d'Archiac and Haime. The band is broad 

 and subcordiform in shape, defining a rather tumid and longitudinally subcarinate 

 subanal plastron, the transverse diameter of which is only a little greater than the 

 longitudinal. About five pairs of pores are included on either side of the area, and 

 the associated granulation is very regular in arrangement, — shallow furrows radiating 

 from each of the pairs of pores towards the centre of the plastron, and the intermediate 

 spaces being ornamented with a row of primary tubercles, which increase gradually in 

 size as they recede from the fasciole, the rows being further marked out by a com- 

 panion row of small uniform miliary granules. This plastron has the appearance of 

 being divided into two areas by a narrow semicircular naked band, which limits the 

 rows of tubercles above mentioned ; and the ornamentation within the subcrescentic 

 area lying between this band and the adoral margin of the fasciole consists of rows of 

 tubercles radiating towards the anus and diminishing rapidly in size as they approach 

 the fasciole. In this manner a very ornate character is given to the subanal plastron. 



The actinal plastron is very remarkable ; it is subcarinate, and terminates posteriorly 

 in a sharp and very prominent peak or culminating point, whilst the profile-outline of 

 the longitudinal keel is incurved between this point and the peristome; the tuber- 

 culated portion of the plastron is very small in consequence of the wide naked posterior 

 ambulacra!' areas, and the tubercles diminish in size in its neighbourhood. There is 

 some depression around the peristome, and the surrounding test has consequently a 

 rather tumid character. 



In large adult tests the odd posterior interradium on the abactinal surface is tumid 

 and roundly carinate, forming a more or less elevated keel between the posterior pair 

 of petals, as shown in Figs. 10 & 11 ; but this character is not developed in small tests. 



