330 THE FOSSIL ECHINOIDEA 



apical system. The plates of the ambulacral petals are very numerous, the inner pores 

 are in broad ellipses, the outer are long and narrow. But the plates of the interradia 

 are large and have a remarkable contour near the apical system. The adoral and 

 aboral edges of the coronal plates are not transverse to the median interradial line, but 

 oblique, and they are not straight, but are in curves, vs^ith the convexity adorally ; more- 

 over the median sutural lines are in bold curves, so that the appearance of the plates 

 is that of imbricating scales. There was, however, no overlap. See Fig. 7 on 

 Plate LI. 



Unfortunately the under surface of the test is eroded. The internal structure of 

 the test is indicated on the worn upper surface, where the peculiar markings so 

 characteristic of the genus are well seen. 



Locality. Gaj series or Miocene of Sind : Naig-Nai valley, twelve miles S. of Shah 

 Rhui. Survey number G '^^- 



Illustrations of the Species in Plates LI and LII. 



Plate LI. 



Fig. 7. Portion of an interradium and of ambulacra: slightly magnified. 



Plate LII. 

 Fig. 1. The test : natural size. 



2. Apical system : magnified. 



3. Part of an ambulacrum : magnified. 



8. A portion of an ambulacrum and lunule : slightly magnified. 



The shape of this species is very characteristic, and its great expansion and very 

 depressed form are extreme in the genus. 



The lunules are very broad and the form is unlike any recent kind. 



The next two species of Echinodiscus belong to quite a different series, for they 

 are either almost circular or ovoid in shape, with the greatest width in front. 



4. Echinodiscus bllipticus, Duncan & Sladen. Plate LI, Fig. 11. 



The test is exceedingly flat, nearly circular, being 68 miUim. in length and 66 miUim. 

 in breadth. The apical system is only very slightly excentric in front and is sub-central. 

 The petals are subequal, rather narrow, and are very slightly swollen. The rosette 

 occupies 38 millim. of the 66 millim. of the breadth. 



There are two lunules and they are long elliptical in shape. 



The anterior margin of the very thin test is slightly incurved and the posterior 

 appears to have been rounded off. 



Locality. Gaj series or Miocene of Sind : Scarp of the M61 Plateau, W. of Kund. 

 Survey-number G -j^. 



Illustration of the Species in Plate LL 

 Fig. 11. The test : natural size. 



