158 Cincinnati Society of Natural History. 



ber differing in different arms), and again on the eighth and ninth 

 above these in most of the rays, the precise number of arms so divid- 

 ing not being well shown. Each of these bifurcating plates, like the 

 brachials, bears a spine which points outward and upward. Many of 

 the intermediate plates bear spines much more delicate and inconspic- 

 uous. All the arm plates are cuneiform and either spinous or tuber- 

 CLilate. 



PinnulcB — These were composed of short, comparatively heavy 

 joints, deeply excavated hy the ambulacral groove. 



Ventral Sac — Balloon shaped, and extending nearly to the tips of 

 the arms. It is quite diff'erent from that of typical PoteriocrinuSj 

 and indicates, according to Mr Wachsmuth, " a link toward Coelio- 

 crinus.'''' 



Column — Small, round, formed of alternately larger and smaller 

 pieces, giving it much the appearance of that of Glyptocrinus. Canal, 

 round. 



Locality and Position — Pulaski county, Kentucky, Kaskaskia 

 (Chester) Group. Sub-carboniferous. 



Remarks — This species is rare, but three specimens having been 

 found. It is readil}^ referred to Scaphiocrinus^ as defined by 

 Wachsmuth and Springer, except by the form of the ventral sac. It 

 seems not impossible that this organ will be found to possess much 

 higher systemic value than has hitherto been given it. 



POTERIOCRINUS ANOMALOS, U. Sp. 

 (Fig- 6, azygous side; 6rt, symmetrical side; 6&, basal view, all three diameters,) 



Under hasals — Not present, or concealed by the column. It is most 

 probable that the latter is the case. 



Hasals — Five, four pentagonal, about as wide as high, pointed above, 

 with the exterior surface convex, somewhat more tumid in the central 

 part. The fifth basal, being that on the az^^gous side, is heptagonab 

 enormousl}" developed, being much wider and higher than either of the 

 others, and extending in the latter direction, as may be seen in the 

 figure, nearly to the top of the radial series, two plates of which it 

 widelj^ separates on this side. I have seen no case of this kind in any 

 other species of crinoid that has fallen under my observation^ and it 

 may be a good generic character. 



Jiadials — Five, three pentagonal, alike in shape and size, wider than 

 high, pointed below, truncated above, the articulating surface being- 

 straight and extending entirel}' across the upper face of the plates. 

 The two adjacent to the azj^gous side have the truncated lower side 



