242 THE FOSSIL ECHINOIDEA 



sized primary tubercles on circular disk-like scrobicules, all equal sized, and so closely 

 placed that only one or two isolated miliary granules are'present here and there. 



Unfortunately no further observations are possible on this very interesting fossil, 

 and under such circumstances we are obviously unable either to formulate a generic 

 diagnosis, or even to draw any useful comparisons with other known forms of Spa- 

 tangoids. 



The length of the fragment, which is incomplete, measures about 75 millim. 



Locality. In the Khirthar series of strata : Eois Hill, near Damaj, south of Bula 

 Khan. Survey-number '^^. 



Illustration of the Specimen in Plate XXXIV. 

 Fig. 17. Abactinal view of the test: natural size. 



IV. Bemarks on the Genera and Species of the Khirthar Series. 



Seventy species and varieties (including 3 doubtful forms evidently placed by 

 mistake in this collection) have been described in the preceding pages. 



The number of species of regular Echini is remarkably small, six only, belonging 

 to five genera, being recorded. One of these, the Temnechinus Bousseaui, appears to us 

 to have been unquestionably included accidentally, and should consequently be excluded 

 from the Khirthar fauna ; this leaves five species of regular Echini in the Khirthar 

 series, representing a numerical proportion of only 7"46 per cent, in relation to the 

 irregular forms, the latter being 62 in number when the 2 doubtful species are excluded. 

 This shows a very striking difference when compared with the underlying Eanikot fauna, 

 in which the proportion of regular forms stands at the high figure of 42-85 per cent. 



The predominant form of regular Echini, as far as may be judged from the number 

 of specimens in the collection, is a species of Micropsis of small habit, having structural 

 alliances to the M. Mokattanends from Egypt, and of which it is probably the Indian 

 representative. The form has also much resemblance to Cyphosoma superhum from San 

 Giovanni Ilarione ; the differences which separate the two species generically being of 

 the most trivial character. 



Of true Cyphosoma there are two well-marked species, one of them being probably 

 nearly allied to the form erroneously referred by d'Archiac and Haime to the genus 

 Echinometra, under the name of ^. Thomsoni; both are comparatively weakly developed 

 forms, of the type in consequence of the small size of the tubercles and the simple 

 ambulacra. 



The Cidaris (Leiocidaris) is closely allied to C. Verneuili of the Eanikot series, of 

 which it is probably the descendant. It is, however, specifically distinct. 



The Porocidaris is more nearly related to the recent forms than to P. serrata, which 

 occurs in the Egyptian and Swiss Nummulitic beds. The pits in the scrobicules are 

 comparatively feebly developed, and, as in the recent forms, do not perforate the test. 

 It was suggested by Sir Wyville Thomson that the fact of their doing so in the case 



