58 THE FOSSIL ECHINOIDEA 



Illustrations of the Species in Plate XIII. 



Fig. 2. Actinal aspect of the test : natural size. 



3. Apical disk and part of the sun-ounding portion of the abactinal surface : 

 magnified. 

 Also a portion of the poriferous zone : more highly magnified. 



Numerous specimens of a Plesiolampas from -^ inch to nearly IJ inch in length 

 were found at a spot north by east of Petiani, west of Kotri ; on hills east of Lynyan, 

 from the brown limestone and gypseous shales, in the Eanikot series. 



Every stage of growth from a minute globular and slightly elongate forni to a 

 depressed ovoid (the adult shape) is represented in the series of specimens ; and in all 

 there is a large, open, transverse, elliptical peristome, a large ovoid periproct placed 

 longitudinally, marginally, or submarginally, and short, open ambulacra placed eccen- 

 trically in front of the centre. The floscelle is feebly developed. The adult form may 

 be taken as the type. 



3. Plesiolampas ovalis, sp. nov. Plate XIV, Figs. 4-18. 



The test is moderately thick in substance ; and its marginal outline is ovoid, with 

 a slight enlargement behind the centre on either side, and a slight blunt point where it 

 is narrowest behind. 



Above, the shape is slightly convex, and rather flat at the vertex and median line ; 

 the margins are well rounded, especially anteriorly. The highest point is rather behind 

 the centre of the upper part, but the slope is very gradual from it. Beneath, the 

 surface is slightly concave, especially near the peristome. 



The apical system is eccentric and in front of the centre ; the generative pores are 

 four in number, and surround a well-developed, convex, madreporic body. The ambu- 

 lacra are subpetaloid, are open at the end, and show but a slight disposition to close ; 

 and the perfect poriferous zones end far from the margin. The anterior ambulacrum 

 is the shortest and usually the narrowest ; it is widely open anteriorly, has a narrow 

 interporiferous zone, and equally developed poriferous zones. The pores, as in the 

 zones of all the ambulacra, are conjugate ; the outer series are the largest, and are 

 round in worn specimens, rather elongate when well preserved. The inner are 

 smaller and rounder. This ambulacrum, like the others, is very slightly raised 

 above the level of the test, and its zones are of equal length, or one may have one pair 

 of pores more than the other. 



The ocular pore, as is the case in the other ambulacra, is small, and the first three 

 or four pairs of pores are exceedingly small and close, so that a small space exists around 

 the apical disk, where, in all the ambulacra, there appears a defective poriferous develop- 

 ment. The pores become fully developed in all the ambulacra in about one quarter 

 the length of the zones. 



The antero-lateral ambulacra form the sides of a very open angle ; they are more 

 petaloid than the others, and their interporiferous zones are the largest. They, are 

 shorter than the posterior ambulaca, which are open and form an acute angle, and 

 terminate far from the end of the test. 



