196 JHE FOSSIL ECHINOIDEA 



Illustrations of the Species in Plate XXXIV. 



Fig. 1. Abactinal view of the test: natural siz6. 



2. Longitudinal profile of the test : natural size. 



3. Transverse profile, seen from the front : natural size. 



4. Apical disk : magnified. 



5. Portion of the odd anterior ambulacrum : magnified. 



6. Portion of one of the antero -lateral petals : magnified. 



7. Ornamentation of the test near the ambitus in one of the anterior inter- 



radia: magnified, 



2. Hemiastee nobilis, BvMcan & Sladen. Plate XXXIV, Figs. 8-11. 



Test of large size ; marginal contour ovally subcordiform, somewhat flattened in 

 front, and very faintly incurved in the region of the odd anterior ambulacrum. The line 

 of greatest breadth lies across the centre of the test, and is proportional to the length as 

 0*93 : 1. Behitid this line the contour contracts gradually, its outline forming a sub- 

 parabolic curve. 



The apical disk is excentric posteriorly, and the greatest height of the test lies a 

 short distance behind this. The condition of the specimen unfortunately does not admit 

 of these proportions being determined accurately, but, as far as judgment can be drawn 

 from the example in its present state, the height appears to have been about three fifths 

 of the length. Seen in longitudinal profile, the keel of the odd posterior interradium 

 does not stand at a higher level than the keels of the lateral interradia, and the posterior 

 slope of the test at a short distance from the apical disk slopes down rather abruptly, 

 with a steep incline to the posterior margin. The anterior slope is much more 

 gradual, and, after a slight curve near the apex, is straight until it reaches the very 

 thick and tumid anterior margin, on which some gibbous protuberances are noticeable. 

 The posterior margin was probably thick, but much less than the anterior margin, and 

 was probably rounded. Seen in transverse profile, the lateral slopes of the dorsal 

 surface are much less inclined than in H. apicalis, and the lateral margins are also very 

 much thicker. 



The odd anterior ambulacrum is in a very wide groove, rather deep in the middle 

 portion of its course, but becoming shallower as it approaches the margin, whilst at the 

 ambitus its presence is indicated only by the faintest incurving of the outline, and is 

 continued in a similar indefinite manner towards the peristome. The pairs of pores, 

 which are situated in small and rather deep oval cavities, are placed obliquely, and the 

 pores of a pair are separated by a rather elongate and pointed granule or tubercle. Near 

 the apex the pairs of pores are very closely placed, but become more widely spaced as 

 they proceed outward, and become single (or apparently so), very widely spaced, and 

 almost microscopic in size beyond the fasciole. The floor of the groove is covered with 

 a minute but rather well-spaced granulation. 



The antero-lateral petals are large, long, and in wide deep grooves, of almost uni- 

 form breadth, except near the apex, and with their outer extremity well rounded. 



