34 THE TERTIAEY FOSSIL ECHINOIDEA 



Nummulitic series of Kachh, which at first sight might be associated with Linthia ; but 

 it is perfectly evident in one specimen, which is admirably preserved in the region 

 around the ambulacra, that there is only a peripetalous fasciole present, the lateral 

 and posterior ambulacra are in deep grooves, and the apical system is central. The 

 form must therefore come into the Hemiasters. 



1. Hbmiastee decipiens, Duncan & Sladen. Plate VI, Figs. 3-5. 



The test is slightly longer than broad and broader than high ; the apical system 

 is small and central, details lost. The anterior margin is very slightly notched by the 

 shallow groove for the odd ambulacrum, which deepens towards the apex. The broad 

 and slightly concave floor of the ambulacrum is ornamented with miliaries, which 

 enlarge near the pairs of pores ; these, some 15 in number, are placed at the rise of the 

 side of the groove, and are separated by low costse. The pairs of pores have a tubercle 

 between them ; there is some distance between the end of the regular series of pairs 

 and the fasciole, and but one pair is found in it. 



The antero-lateral ambulacra are long, nearly straight, only bending slightly with 

 the convexity forwards and inwards, and are in deep and rather narrow grooves, which 

 become shallow distally. The greatest breadth is at two thirds -of the distance from 

 the apex, and the poriferous zones nearly close, being cut across by the fasciole. 



The interporiferous area is nearly, if not quite, as broad as the poriferous zone in 

 the centre of the petal, and is narrower than it further out. 



The poriferous zones are on the slope of the sides of the groove, are very slightly 

 sinuous, and the anterior is slightly more curved than the posterior. The pores are 

 large, oval, subequal, and are conjugate, and each pair is separated from its neighbours 

 by costse with a line of distinct miliaries on them. The pores suddenly become small 

 towards the apical system, and there are thirty-two pairs. Length of ambulacrum 21-5 

 millim., breadth of groove 6 millim. The ambulacra form an angle of about 110°. 



The postero-lateral ambulacra, shorter and narrower than the anterior pair, are 

 closer together, nearly straight, and are in deep grooves. The interporiferous area is 

 rather narrower than the poriferous zone, and its details resemble those of the corre- 

 sponding areas of the antero-lateral petals. There are 29 pairs of pores ; and the length 

 of the petals is 17 millim. and the extreme breadth is 4 miUim. The distal end is 

 more pointed than that of the antero-lateral ambulacra. 



The keels of the interambulacra at the apex are not pronounced, and those of the 

 lateral interambulacra are rather wide. The fasciole is widely spread, and is wide and 

 well developed; it is large at the extremity of the lateral petals, enters but slightly 

 withm the lateral interambulacrum, and passes directly over the posterior interambula- 

 crum m a straight line. In front a large space is included by the fasciole, for it crosses 

 the anterior ambulacrum not far above the ambitus on a curve, convexity forwards 

 and It starts off on either side to the end of the long antero-lateral petal 



The ornamentation within the fasciole is very close and small, and consists of low 

 tubercles, perforate and crenulate, surrounded by a circle of mUiaries ; it is very 



