OF WESTEKN SIND. 43 



where they rapidly dimmish in size. The costse radiate from the base of the boss, 

 cross the scrobicule, and have a miliary tubercle on them at the circle-edge. Three 

 or four costse placed close together in a band, unite the tubercles of the same vertical 

 series, and two bands of two or three costse, each ornamented with a miliary, pass off 

 obliquely to unite with corresponding costse from the two opposite tubercles. Four 

 or five costse pass to the poriferous zone, having miliaries here and there, and they 

 join the perforated costse of the ambulacra. 



Other costse occur in the intervals between all these and the bands, and thus a 

 zigzag series of narrow, shallow, and broad spaces is produced. The peristome is very 

 small, and the cuts also. 



Height of the specimen -^g inch, breadth ^g inch. 



Locality/. North by east of Petiani, west of Kotri, in the Ranikot series. Survey- 

 number G f f ^. 



Illustrations of the Species in Plate IX. 



Fig. 6. Arachniopleurus reticulatus, Duncan and Sladen : natural size. 



7. Part of an ambulacrum and interradium : magnified. 



8. Some ridges near the apical disk: magnified. 



Genus PEOGONECHINUS, gen. nov. 



Test of small size, moderately high, subcorneal above, concave beneath, margins 

 tumid. 



Poriferous zones straight, pores arranged in simple continuous series throughout. 

 Ambulacral plates with three pairs of pores directly superposed. Interporiferous areas 

 with two vertical series of primary tubercles placed marginal ; additional primaries 

 occurring on the plates near the ambitus ; the rest of the plate occupied with granules. 

 Interradial plates with groove-like slits at the inner extremity of the horizontal sutures. 

 Interradial areas with two continuous vertical series of primary tubercles, the plates 

 at the ambitus with two or more companion primaries in horizontal line, the vertical 

 series of these being not continuous. The primary tubercles of both areas are neither 

 crenulate nor perforate ; those of the interradia are slightly longer than the ambulacral 

 tubercles, and are sunken in deep scrobicules. Granulation coarse and unequal, with a 

 tendency to become confiuent around the tubercles. Some larger granules with 

 mamelons. Apical system unknown. 



Peristome subcircular, with rather deeply incised slits, with margins thickened and 

 reverted. 



1. Pkogonechinus EocenicdSj Duncan & Sladen. Plate X, Figs. 1-4. 



The test is depressed, swollen at the ambitus, and sloping convexly to the apex. 

 The actinal margin is rather pentagonal, the median interradial and ambulacral vertical 

 lines are slightly depressed, and the spaces on either side are rather tumid. The extra 



