326 Cincinnati Society of Natural History. 



two thirds being bent on the lower so as to stand nearl}' at right 

 angles to it in the natural position of the specimens, and forming the 

 side boundary of the almost tube-like basal depression. The upper 

 end of four of these plates is acutel}^ oval, so that this extremity can 

 onl}' be said to have two faces by virtue of its occupj'iug a concavity 

 formed by the excavated faces of the contiguous radials. The sides of 

 the vertical two thirds of these plates are concave toward the stem, or 

 columnar cavit}^ and are seen to be convex inwardly in section. The 

 fifth is similar to the other four, except that its upper extremity is 

 truncated for the support of the second az3'gous plate, and that it is 

 somewhat larger. These plates form a five-leaved flower-like base, 

 similar to that seen in true Zeacrinus. 



Radials — Five, somewhat wider than high, pentagonal, nearly equal 

 in size and shape, that on the right of the azygous area resting upon 

 one basal, the others resting upon two. These plates are convex and 

 thickened outwardl}', and separated from the brachials by wide ex- 

 ternal sutures. 



Brachials — Five, four pentangular, that oppos'ite the azygous area 

 quadrangular; the first four are spiniferous, and from their position, 

 and the size of the spines, give the basal view of the specimens a 

 quadrate outline as seen in fig, 4. These plates meet lateral h^, and 

 each bears upon its upper sloping sides the large quadrangular first 

 arm-plates, which are wanting in case of the other, upon the upper 

 sides of which rests a series of small plates, such as follow the large 

 arm plates in the other foui'. 



Arms. — The ten arms, resting upon the brachials, are divided as fol- 

 lows, above these plates, the divisions always taking place on the 

 sides opposite the sutures between the brachials, or toward the suture 

 joining the large arm plates resting upon each brachial. The first 

 pair of arms on the right of the azj-gous area gives rise to nine arms, 

 five on the left and four on the right; the second pair to nine in the 

 same manner. The first pair on the left of the azygous area to nine 

 arms, five on the right and four on the left; the second pair to nine in 

 the same manner. 



The remaining pair, which is that opposite the azygous area, gives 

 rise to six arms, three upon either side. These subdivisions, very per- 

 fectly shown in the specimen, are not so well indicated in the figures 

 1 and 2. This is as far as the divisions of the arms can be traced, and 

 it gives us 42 arms at the free extremities. Each new subdivision 

 rests upon a large spine-bearing plate, the articulating surface sloping 

 toward the dividino' side. This arrano-ement renders the sutures con- 



