:}6 



Cincinnati Society of Natural History. 



the arm, and each of which supports at its larger end a pinnule. The 

 pinnules are long and very slender, and composed of long-jointed 

 pieces. 



Column. — The column is round, and composed of alternately thicker 

 and thinner plates. These project beyond the parts of contact, the 

 thicker plates project beyond the thinner ones, as is usual in other 

 species of this genus. As we recede from the head the larger plates 

 are more distant from each other and project less. The column en- 

 larges a little as it approaches the head. The column, in our speci- 

 men, is half embedded in rock, and we have no fragments for examin- 

 ation, hence other peculiarities and distinguishing characters must 

 await some future definition. 



The specimen described is from the magnificent collection of I. H. 

 Harris, Esq., of Waynesville, Ohio, and is from the upper part of the 

 Hudson River Group, at that locality. 



Remarks. — Messrs. Wachsmuth and Springer seem to have been 

 practically unacquainted with this genus, as their diagnosis requires 

 that the surface of the plates should be " ornamented with radiating 

 striae in form of elevated ridges which divide into numerous triangular 

 impressed areae;" that the basals should "scarcely extend to the sides 

 of the body;" that the second radials should be "hexagonal;" that the 

 third radials should be " pentagonal," and as to the succeeding plates 

 the diagnosis would include those of almost any other genus in the 

 family; and having "arms twenty." The above described species 

 would not be included in their diagnosis, and yet I have not the least 

 doubt that it is a true Glyptocrinus; it may be that they would refer 

 it to Reteocrinus, or propose for it a subgeneric name, — neither course, 

 do I think, would be warranted, with our present kuowledge of the 

 structure of crinoids; and this possible reference may justify a few re- 

 marks upon Billings' genus. 



The genus Reteocrinus was described by Billings, as consisting of a 

 reticulated skeleton, composed of rudimentary plates, each consisting 

 of a central nucleus, from which radiate from three to five stout pro- 

 cesses. Of such plates there are five in the basal series, five in the 

 sub-radial, and five in the radial series. On the azygous side the sub- 

 radial has five processes; the others have four each. The type species, 

 R. stellar is, is well illustrated (plate IX., figs. 4 and 4a, Can. Org. 

 Rem. Decade IV.), showing these characters. The azygous subradial 

 has five processes, three above and two below. The first primary radial 

 in the right anterior ra3' has three processes, the upper one of which 



