92 DAVENPORT ACADEMY OF NATURAL SCIENCES. 



Radials small, body-part longer than usual in this genus, their lower 

 portions resting within the concavity, whence they bend abrui)tly in 

 an opposite direction, forming a sharp edge at the end of the body. 

 Length more than twice the width at the basi-radial suture, which is 

 about equal to the width of a limb at its upper side. Sinus very short, 

 enclosing but little more than the lip, which is strongly protruding, and 

 from which a very prominent rounded ridge proceeds to the lower edge 

 of the plate. 1 he upper sides of the limbs are convex, with a reen- 

 tering angle above the lateral sutures. 



Interradials large, occupying four-fifths of the length of the entire 

 body, divided by two raised lines into three parts, the inner or deltoid 

 part provided with fine granules, the outer part with transverse grooves, 

 which are ec^ual to the number of side-plates in the ambulacra. The 

 anal plate, which divides the posterior interradial, differs in form but 

 little from the deltoid-sha])ed portions of the other four interradials; it 

 is, however, a little wider, and at the upi)er end protruding outward. 

 The anal aperture is large, rhomboidal, the opening in an upward 

 direction. It is bordered toward the peristome by two summit plates, 

 which rest against the upper ends of the two sections of the interradial. 



Ambulacra linear, comparatively shorter and probably wider than in 

 any other species of Elceaa-inus ; lancet-piece exposed within the food- 

 groove, but only at the ui)])er end of the plate, its lower half is per- 

 fectly covered by the side-plates. There are 36 to 38 side-pieces 

 (outer side-pieces cannot be distinguished in the specimens), with a 

 deep socket to each plate. The hydrospire-i>ores are only seen when 

 the side-plates are broken away. 



Spiracles ten, one to each side of the ambulacrum; slit-shaped, 

 placed, like those of the preceding species, within the projecting lateral 

 edges of the interradials; those of the anal side non-confluent with the 

 anal aperture. The hydros])ires are unknown. 



The summit (which in both type specimens has been ])reserved) is 

 composed of but few comparatively thick pieces, which are similarly 

 arranged as in Khvacriiiiis oboTotus. Column round, central perfora- 

 tion very small. 



Ohscnuitions : This s])ecies has its closest affinity with Rhvaci-inns 

 (Niicleocrinus) clei:;ans Conrad, from which it difiers in the more 

 elongate form, in the mode of ornamentation, in having almost straight 

 in place of concave interradial sides, and in the less i)rotruding and 

 comijaratively shorter ambulacra. The latter, in Conrad's species, 

 reacli to the truncate portion of the body, while in E. vieloniforjnis 



