OF WESTERN SIND. 19 



lanceolate or elongately ovate, their distal ends being crossed by the fascicle. 18 or 

 19 pairs of pores exist in each zone ; and the interporiferous area is narrow. The inter- 

 ambulacra are slightly swollen and formed into ridges near the apex and on either side 

 of the anterior groove, the posterior interambulacrum being also elevated into a slight 

 keel. 



The ornamentation of the test is slight and inconspicuous, the tubercles being very 

 small. A few rather larger ones are scattered on either side of the anterior groove, 

 and accumulate on the anterior slope of the test. Smaller tubercles are distributed 

 uniformly on the dorsal surface of the test, except near the ambulacra and apex, where 

 they are slightly larger and more crowded. Surrounding the posterior truncation the 

 tubercles become larger and scarcer inferiorly, and above on either side of the periproct ; 

 but below the aperture they are almost, if not quite, wanting. 



Periproct oval, vertical, and placed high up on the truncated end of the test. 



The peristome is small, placed far in front and near the margin, the anterior 

 groove being distinctly continued up to it. The lip is not prominent, the neighbour- 

 hood of the mouth is rather impressed, and the plastron is rather swollen — circumstances 

 which, together with the tumid character of the margin, relieve the flatness of the 

 under surface. The ornamentation of the plastron consists of a few large and many 

 small tubercles ; and the sides of the test beneath have larger tubercles than the rest of 

 the test. The tubercles below are crenulate and perforate, the slightly sunken scrobi- 

 cule being surrounded by a sparely filled circle of small miliary granules. 



The peripetalous fascicle is very narrow, and forms an angle in the interspace 

 between the lateral ambulacra, reaching up halfway to the apex. The fascicle turns 

 round the anterior lateral petal, passes inwards parallel with it, forming the angle just 

 mentioned, and then crosses over to the posterior lateral petal, coming into contact with 

 its outer pores, and crossing directly over the keel of the posterior interambulacral area 

 to the opposite side. In front the fascicle crosses the anterior odd ambulacrum a little 

 below the line of the end of the antero-lateral petals ; but it is very small and indistinct 

 in this portion of its course. A lateral fascicle commences where the peripetalous 

 fascicle begins to pass inwards, a little behind the end of the antero-lateral petal, and 

 extends in a very thin and slightly raised line directed backwards and downwards 

 and passing under the periproct to the other side. 



Memarks. Idnthia Sindensis is characterized by its general rotundity of margin, 

 its equal length and breadth, its greater breadth in front, its moderate height, and the 

 gentle declivity of the dorsal slope, its deep anterior groove (which is very decided at 

 the margin), and the anteriorly excentric position of the apical system, by the number 

 of close pores in the anterior ambulacrum and the comparative length of the postero- to 

 the antero-lateral ambulacra (as 2 to 3), by the narrowness of the interporiferous zone, 

 and by the very narrow and slightly bent fascicle (which is comparatively faintly angu- 

 lated, excepting its sharp dip far below the oval periproct). 



This Echincid is, on the whole, rather more closely allied to Cretaceous than to 

 Nummulitic forms. The Sindian species differs irova. Periaster pyrenaicus, Cotteau (its 

 nearest ally), in the shape and proportions of the ambulacra, the greater lateral 

 rotundity of the marginal contour, the greater depth of the anterior groove, the form 



