146 PALAEONTOLOGY OF NEW- YORK. 



one elongated and very unequally five-sided; the lower angular ex- 

 tremity resting one side against the long basal plate of the concave 

 side, and the opposite shorter side resting upon the sloping edge of the 

 adjoining basal plate of the convex side. The second radial plates rest, 

 one side against the lateral margins of the large central plate of the 

 concave side, and the opposite sides adjoin the plates of the convex 

 side ; thus, with the base and summit, giving one of those plates an 

 irregular hexagonal and the other a heptagonal form. Third radial or 

 angular plates heptagonal. Fourth radials imknown. 

 Column unknown. 



This very anomalous form does not correspond in structure with any described 

 species of cystidian or crinoid. The body is in form like some of the ovoid cystidians 

 or crinoids cut longitudinally through the centre; and a little depressed on that 

 side, with strong bent plates at the angles. The arrangement is distinctly in four 

 series; the two lateral or angular plates corresponding, while the posteal and anteal 

 series are very unlike in form, number and arrangement. The summit is broken 

 off; so that the organs of mouth, ovarian opening, etc., remain undetermined. 

 There are three plates preserved in each lateral series; and there was evidently a 

 fourth, which probably supported spines similar to those observed in the other 

 species, and which seem to be the only representation of arms or tentacula in this 

 form of cystidian. 



The specimen figiu-ed has suifered no distortion, and the figures represent no more 

 of the structure than can be seen distinctly. The basal range of plates on the posteal 

 side are only partially preserved, and are described in part from the form of the 

 spaces remaining, and from the corresponding parts in the other species where well 

 preserved. 



Fig. 1. Anteal or concave side, showing the deeply arched or crescentform base with the 

 succeeding plates. 



Fig. 2. Posteal or convex side, showing form and arrangement of plates. 



Fig. 3. Lateral view of the same specimen. 



Fig. 4. Diagram illustrating the structure of the body, showing the deep indentation for the 

 insertion of the column : a, plates of the anteal or concave side ; p, plates of 

 the posteal or convex side ; r, r, the lateral or radial plates, which are shaded 

 to indicate the abrupt angles, one part of the plate serving to make up the 

 convex and the other the concave side. 



Geological positim and locality. In the Oriskany sandstone : Cumberland, Md. 



