THE TEKTIAKY FOSSIL ECHINOIDEA 



Genus ECHINODISCUS, Breynius, 1732. 

 This genus, under the careful study of Alex. Agassi z, has absorbed the genera 



Loh(yphora and Amphiope. 



The test is much depressed and thin ; the anterior edge is rounded, and the pos- 

 terior is truncated. There are two lunules or cuts corresponding to the posterior ambu- 

 lacra. Ambulacral petals small and well defined. Four genital pores. Lower surface 

 flat, and the ambulacral furrows ramify but little towards the edge. Anus near the 

 posterior edge. The greater part of the interior is occupied by a calcareous network 

 rising into pillars for more than half the distance between the edge and the actinostome*. 



In the Miocene series of Kachh there are some imperfect specimens of a small 

 member of this genus ; but they are sufficiently well preserved to give specific characters, 

 which show that they differ from, and yet are closely allied to, Echinodiscus Mforis, 

 L. Agassiz, sp., from Mozambique, the Red Sea, and Java. 



1. EcHiNODiscus Desgei, Buncan & Bladen. Plate XII, Figs. 7-10. 



The test is very thin, broader than long, broadest on a line with the distal ends of 

 the posterior ambulacra; it is narrower and rounded in front and broadly rounded 

 behind. Actinally, the test is flat and the actinostome is very small and nearly central ; 

 abactinally there is a very faint projection of the rosette and apical system, which 

 is subcentral or slightly posterior. 



The anterior odd ambulacram is the longest, and is narrower than the antero- 

 lateral petals, which are the broadest. The posterior petals are broader and shorter 

 than the anterior, and smaller altogether than the antero-lateral petals. The petals are 

 short and closed, and the rosette is small on the whole. The poriferous zones are 

 broad, and their greatest breadth is at their outer third ; the interporiferous area is 

 about the breadth of one of the poriferous zones. 



The apical system is large in comparison with the petals, and there are four genera- 

 tive pores : the front pair are distinct from the others, and are slightly closer together 

 than are those of the hinder pair. The posterior pores are external to the position 

 of the antero-lateral ocular pores. 



The lunules behind and in a line with the posterior ambulacra are in ellipses, 

 whose long diameter is not quite three times that of the minor. 



Actinally the grooves are broad and shallow ; they bifurcate close to the mouth, 

 curve symmetrically, and enclose long elliptical spaces, and give oflf" a side branch near 

 the edge. Each groove has a raised ridge on its floor near the peristome, which ends in 

 a slight swelling perforated by two lenticular pores. 



The peristome is longer than broad, and the interambulacra are slightly raised at 

 its edge, the posterior being the broadest. 



Locality. Miocene series of Kachh : three miles north-west of Kayari, near 

 Narainsir. Survey-number C 038 f. 



* See Ales. Agassiz, ' Revision of the EcWni,' p. 531. 



