144 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



Dome apparently composed of five triangular plates, their broad 

 bases resting on two adjacent radials. The sutures of two sum- 

 mit plates unite over the middle of the radial plates, and have 

 the lower lateral angles truncated, forming the upper border of 

 the arm-openings. The summit-plates have grooved sutures, shal- 

 low in the lower part and becoming deeper above, truncating the 

 top of the pyramid : when viewed from above, these grooves 

 form a five-pointed stellate depression. 



Surface of plates marked by fine, wrinkled, radiating striae. Sutures 

 in the calyx slightly impressed below, and more strongly near the 

 top of the radial plates, the margins of which are thickened and 

 the upper edges rounded over into the summit. 



The arms appear to have been composed of long slender plates, 

 articulated by a mitred end to the sloping cicatrix of the radial 

 plate. The inner face is strongly grooved, corresponding to the 

 size of the opening into the cavity of the body. 



Geological formation and locality. In limestone of the Marcellus sliale: 

 Onondaga county. C. A. White, collector. 



GENUS NUCLEOCRINUS (Conrad). 



Nucleocrinus : Conrad, in Journal Acad. Nat. Sciencesj Philadelphia, Vol. viii, 

 pa. 280, pi. 15, f. 17. 1843. 



Olivanites : Troost, MS.; and in Catalogue of Crinoidea, Trans. Am. Association 



for the Advancement of Science, 1849, p. 

 Elaacrinus : F. Rcemer, 1852. 



The description of this genus by Mr. Conrad in 1843, though very 

 imperfect, is nevertheless accompanied by a figure, which sets at 

 rest all question as to the fossil intended. The Mucleocrinus elegans 

 (^ loc. cit. p. 280) is the one referred to as JV*. halli by Vanuxem 

 ( Report, p. 163), the latter name having been first applied to the 

 species by Conrad. 



I am not aware at what time the name Olivanites was first pu- 

 blished by Troost, though I believe no description was ever given 

 by him. In the Geological Report of Tennessee for 1841, the species 

 ( G.) verneuili^ afterwards made the type of the Genus Olivanites, 

 is placed under the Genus Pentremites. In 1849, the name Oliva- 

 nites was published in Troost's Catalogue as cited. The species 

 JVucleocrinus {Olivanites) verneuili, being a comparatively common 

 form in the West, was widely known under the name Olivanites; 

 while the original of JVucleocrinusj being extremly rare, was little 

 known. 



In 1852, Dr. F. Rcemer published his description of El.eacrinus 



