306 THE FOSSIL ECHINOIBEA 



is little or no difference in size between the tubercles of the two areas. The absence 

 of the apical disk is to be regretted. 



Genus LEPIDOPLEURUS, gen. nov. 



Test small, broader than high, nearly hemispherical or turban-shaped. Apical 

 system large, solid ; basals alone enter the anal ring, and are long vertically ; radials 

 perforated at their adoral edge. Ambulacra small ; poriferous zones slightly sunken, 

 pairs in simple series. Interporiferous spaces crossed by a zigzag of raised granular 

 ridges uniting the opposite tubercles. Interradial plates angular, with the adoral edge 

 overlapping and occupying a corresponding cavity in the aboral edge of the plate 

 below. Two vertical rows of tubercles, and the tubercles of each row are connected by 

 vertical and narrow ridges. Peristome and cuts small. Ambulacral plates in triplets, 

 the aboral plate of the composite plate being a low primary; the next below is 

 a demi plate, very small, and crowded out of the line by the succeeding or adoral 

 primary, which has an expanded interporiferous part. 



Tubercles imperforate and not crenulated. 



The angularity and scale-like appearance of the interradial plates, the ridges 

 between the tubercles, and the sunken sutural lines separate this genus from the others 

 of the Temnopleuridse. 



There are two well-marked species of the genus in the Gaj Tertiaries. 



1. Lepidopleueus hemisph^eicus, Duncan & Sladen. Plate XLVTI, Figs. 5, 6, 7. 



The test is small, nearly hemispherical, slightly broader than high, rather flat at 

 the apex, and moderately concave actinally. The apical system is large, flat, and not 

 projecting, solid, and has a wide ring of basals and radials, the last not entering the 

 circumference of the round and open periproct. The basals alone form the anal ring, 

 and they are large, slightly unequal in size, the madreporite being the largest ; there is 

 an adoral angle and seven sides to each plate, the edge in contact with the periproct 

 being one of them. The height of the plates is greater than their breadth at the 

 periproct, and the ovarial pore is large and near the adoral angle. The madreporite 

 has no pore, and the spongy surface is decidedly convex. The sutures of the plates are 

 very distinct, and the slope of the surface of the whole system from the faint ring round 

 the anus to the adoral angles of the basals is slight. 



The radial plates are broader than high, widely separated from the periproct, and 

 are more or less irregularly triangular in outline. The adoral edge of the radial plate 

 is broad, and has a projection at the median line, on either side of which there is a 

 curved edge, the concavities of the curves looking towards the ambulacra. The optic 

 pore is at the base of this projection. 



The ambulacra are narrow, petaloid above, open actinally, and they are about one 

 half of the width of the interradia at the equator ; but at the peristome the breadth of 

 the ambulacra is only a little less than that of the interradia. The surface of the 



