16 FAUNA OF BALUOHISTlN. 



Protbchinus patjcitubbrculattjs, spec. nov. PI. II. fig. 3-3A. PI. III. fig. 1-la; 



The thin, large test is circular, having a diameter of not less than 95 mm. ; the 

 upper surface is highly inflated, apparently a little conical, the lower surface flat, 

 slightly pulvinated at the margin. 



Apical disc imperfectly known, hut apparently not very large : anal opening 

 small. 



Ambulaoral area not very broad, slightly convex, poriferous zones straight, rather 

 broad and trigeminal, pores small, rounded and arranged in a peculiar fashion; the 

 apical pairs of each plate, which form at the same time the inner row, are composed 

 of two minute pores situated on a small elliptical plate, which looks as if it were 

 jammed between two consecutive ambulacral plates ; the two other pairs are com- 

 posed of larger pores of the same size arranged at the four angles of a rhomboid. 



Tubercles very small, but uniform in size, all over the test ; the mammillary 

 eminence is rounded, low, imperforate ; the boss low, not crenuulated, surrounded 

 by a flat, rather large areola which is encircled by a low, smooth ridge. 



On the ambulacral areas there are about 8 somewhat irregular rows of tuber- 

 cles at the ambitus which, extending to the mouth, are reduced to about 4 on the 

 upper surface ; the rows gradually disappear until there remain only the two exter- 

 nal ones which reach as far as the apical disc ; on the interambulacral areas about 

 16 to 18 rows of tubercles may be counted at the ambitus; this number is, however, 

 quickly reduced to about 4 near the mouth and 3 to 4 on the upper surface, of which, 

 however, only two extend as far as the apex. The tubercles are arranged in horizon- 

 tal lines on the interambulacral plates in such a way, that beginning from the apex 

 the number of tubercles on each plate very slowly increases from 1 to about 9 

 near the ambitus, and then equally slowly decreases to about 4 near the mouth. 

 Miliary zones perfectly smooth, except some minute sparsely distributed granules. 



Periproct unknown, but apparently not very large. 



Spines short, very thin and longitudinally striated. 



Locality and stratigraphical position. — Upper cretaceous series, horizon 4, 

 Des Valley. 



Remarks. — Unfortunately none of the specimens is completely preserved ; the 

 thin high conical test was apparently too weak to withstand pressure, and for this 

 reason they are all more or less deformed. I am therefore unable to say whether 

 it is an original feature that the interambulacral areas are slightly concave 

 in the centre ; it is quite possible that this may be so, and then it would be quite in 

 accordance with the slightly convex ambulacral areas. 



