INVERTEBRATES. 361 



ELTEACKINUS MELONIFORMIS, Barris, Nov. sp. 



Body small, ovoid, height nearly one-half more than the width; 

 greatest width through the median part, or a little above ; curvature 

 toward the two poles nearly equal, but the pole itself at the abac- 

 tinal side abruptly depressed, and the concavity perfectly filled by 

 the column. Surface of the ambulacra raised but little above the 

 general plane of the body. The plates along the sides of the am- 

 bulacra are marked with obscure transverse grooves, bordered at 

 each side by a sharp ridge, which forms along the median por- 

 tions of the plate a deltoid-like figure. The ridges which join with 

 one end at the summit, with the other at the radial lips, form to- 

 gether around the body a well marked penta-petaloid figure in which 

 the ambulacra are placed along the median line ; and as the ridges 

 in this species happen to be more conspicuous than the margins of 

 the ambulacra, the ridges appear as the boundaries of the latter. 

 Cross-section along the upper half of the body obscurely decagonal, 

 almost circular, decidedly pentagonal across the lips of the radials. 



Basals small, entirely hidden within the columnar cavity. 



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

 lower portions resting within the concavity, whence they bend 

 abruptly 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. The upper sides of 

 the limbs are convex, with a re-entering angle above the lateral 

 sutures. 



Oral plates 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 trans- 

 verse grooves, which are equal to the number of side plates in the 

 ambulacra. The anal plate which divides the oral piece of the pos- 

 terior interradius, differs in form but little from the deltoid-shaped 

 portions of the other four interradial sides; it is however a little 

 wider, and at the upper end protruding outward. The anal-aperture 

 is large, rhomboidal, the opening in an upward direction. It is 

 bordered towards the peristome by two summit plates which rest 

 against the upper ends of the two sections of the oral plate. 



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