372 THE FOSSIL ECHINOIDEA 



III. Description of the Species of Echinoidea. 



OrtZerECHINOIDEA ENDOCYCLICA. 



Family CIDABIDJS. 

 Genus CIDARIS, Klein, 1734. 



1. CiDAEis, sp. (GomociDAKisI). Plate LVI, Figs. 1 & 2. 



Several well-preserved fragments of a species of Cidaris are in the collection from 

 the Makran beds ; but there is not sufficient material to give a specific character, and 

 indeed the generic position is doubtful. 



Test tall ; ambulacra wide and very slightly flexuous, with ten pairs of pores in 

 relation to a coronal plate at the ambitus. 



Interporiferous part of the ambulacral plates as wide as the poriferous zone, but 

 it is low and ornamented with a small secondary tubercle close to the poriferous zone 

 and with three small granules, two of which are usually in a line and nearer the adoral 

 margin of the plate than the aboral. Sometimes there is a small tubercle placed 

 aborally to the second tubercle. The small secondary is in continuation with, the ridge 

 which separates the pairs of pores. The adoral pore is usually the larger of the two, 

 and there is a distinct and broad partition, convex from above downwards, between the 

 pores of a pair. 



The interradial plates are broader than high, the height diminishing towards 

 the peristome, and the elliptical shape of the scrobicules increases from the ambitus in 

 both directions. The slope of the coronal plates to the median suture of the inter- 

 radium is decided, and there is some sinking at the suture. Sometimes there is a 

 distinct sutural groove between the successive coronal plates. The scrobicular margins 

 are perfect, and are surrounded by a row of small secondaries with rounded maraelons, 

 and usually they are small actinally and abactinally to the scrobicule and separated all 

 round the circle by large granules. The bossis low and has a wide grooved collar ; the 

 mamelon is hemispherical and has a wide neck. There is perforation but not crenulation. 

 There is some sinking of the plates within the raised scrobicular margin. Between the 

 scrobicular circle and the poriferous zone, there is a small row of secondaries close to 

 the larger series and also some granules, and on the other side at least three rows of 

 granules are developed between the circle and the sunken median suture, and on a 

 rather tumid and sloping part of the plates. 



Locality. Henjam Island, Persian Gulf. Makran deposits. Survey-number G ^f^. 



Illustrations of the Specimen in Plate LVI. 

 Fig. 1. A part of a test : natural size. 

 2. Ambulacral plates : magnified. 



