328 THE FOSSIL ECHINOIDEA 



1. EcHiNODiscus Desori, Duncan & Sladen, 1883. Plate LI, Figs. 1 & 2. 



This species was described in the Monograph of the Tertiary Echinoidea of Kachh, 

 and Kattywar (Pal. Indica, Ser. XIV. p. 60, 1883), and was figured on plate xii. of that 

 work. 



This Miocene species is not common in the Gaj deposits, and there are some 

 forms which we cannot but consider as the adults of the species with some variation in 

 their shape. 



In the type from Kachh the anterior petal is longer and narrower than the antero- 

 lateral, the two lunules are elliptical in outline and they are narrow, the long 

 diameter being not quite three times the breadth. The anterior margin is faintly 

 indented and the test is broadest on a line with the distal ends of the posterior ambu- 

 lacra. The breadth of the test is greater than the length, and there is a decided 

 narrowing in front and a broadening out behind. The actinal grooves are broad and 

 shallow ; they bifurcate near the mouth-curve symmetrically, and enclose rather long 

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

 a slight swelling perforated by two tentacular pores. 



A small specimen from the Gaj deposits is figured on Plate LI, Fig. 1, and an 

 outline is given. Fig, 2, of a small form. In both the convexity of the test posteriorly 

 is shown, and it will be observed that there is some difference in the dimensions of the 

 lunules. The length and the breadth of the form represented by Fig. 1 are equal, but 

 the breadth of the form of Fig. 2 is normal, and the breadth is greater than the length. 

 The figures are natural size, and the specimens came from the Miocene or Gaj deposits 

 of Sind. 



Locality. Four miles south-west of Beynir Hill, Survey-number G ^^^. 



Illustrations of the Species in Plate LI. 

 Fig, 1 , The abactinal view of a test : natural size. 

 2. Outline of a test : natural size. 



There is a well-marked variety of the species which we have drawn on Plate LI, 

 Fig. 3. The test is slightly broader than the type, the petals are subequal, and the 

 posterior edge of the test is almost straight. The general shape of the type is not 

 much altered, the lunules are of the same shape and the test is of the same great 

 tenuity. The variety brings the type in close alliance with Echinodiscus Uforis, 

 A. Agass., a recent form from the Eed Sea and East-African coast. 



Illustrations of the variety in Plate LI. 

 Fig. 3. The test : natural size. 



EcHmomscus Desoei, Duncan & Sladen, variety. Plate LI, Figs. 4, 5, 6, 8, 9, 12. 



This variety has all the characters of the species, and the test is also nipped in 

 anteriorly to the widest part, so as to give more or less of a trifoliate appearance. 



