78 THE FOSSIL ECHINOIDEA 



In all the tumid test, the slightly eccentric-in-front and small apical rosette, the 

 more eccentric-in-front and small and transverse peristome, with a well-developed 

 floscelle, the faint keel, and the projecting but low-down periproct and the extra- 

 petalous row of solitary pores are very distinct and characteristic. 



Illustrations of the Species in Plate XVI. 



Fig. 1. The test, from above: natural size. 



2. The test, from below : natural size. 



3. The floscelle and peristome : magnified. 



4. The test, side A'iew : natural size. 



5. I'he posterior end : magnified. 



6. The transverse outline. 



7. The apical system : magnified. 



8. A small specimen, from above. 



9. The ornamentation : magnified. 



10. Part of an ambulacrum : magnified. 



Family SPATANGIBM 



Siihfamih/ SFATANQIKJE. 



Genus HEMIASTER, Desor, 1847. 



The test may be short and inflated, or dilate and cordiform. 



Apical system subcentral, or more frequently eccentric posteriorly. 



The paired ambulacra are petaloid, more or less unequal, placed in furrows ; their 

 poriferous zones are broad and equal, pores elongate. The odd ambulacrum often 

 narrower than the rest, and placed in a less defined groove ; its poriferous zones are 

 very narrow, and composed of very small round pores forming a simple series of widely 

 spaced obliquely placed pairs. 



Peristome bilabiate, very eccentric in front. 



Periproct on the posterior extremity. 



A single fasciole, peripetalous, more or less angular, surrounding the ambulacral 

 petals. 



Tubercles perforate and crenulate, not sunken in scrobicules ; small, uniform, and 

 crowded on the abactinal surface, rather longer on the actinal surface. 



1. Hemiastee elongatus, sp. nov. Plate XIX, Figs. 7-15, 



The test is long, depressed, tumid at the ambitus, slightly convex actinally, rather 

 rounded apically, highest posteriorly, posterior margin slightly truncated above a sharp 

 plastron-point and below the elliptical transversely placed periproct. It is longer than 

 broad, and broader than high. 



