CONTRIBUTIONS TO PALEONTOLOGY. 143 



There are some indications of a division across the middle of the radial 

 plates, passing horizontally through the central perforation; and another 

 from the perforation upward to the arm-openings, making the apparent 

 single plate to be made up of three plates; but these characters are 

 obscure. Should they, however, be proved to exist, it will be necessary 

 to separate this form from the Genus Myrtillocrinus as now defined. 



Geological formation and locality. In limestones of the Upper Helder- 

 berg group : near Caledonia, Livingston county. C. A.White, collector. 



GENUS HAPLOCRINUS (Steininger). 



The following species clearly appertains to the Genus Haplocrinus, 

 if we are to judge from the structure of the body. A single specimen 

 preserves the base of one of the arms attached to the ray; setting at 

 rest the question as to the position and relations of the arms, so far 

 as this species is concerned. Unfortunately, this minute and pretty 

 species occurs in a limestone where the material is much broken and 

 comminuted; and although we have numerous specimens of the 

 body, no other portions are preserved in connection, except in the 

 specimen mentioned. 



Dr. Troost has recognized several species of Haplocrinus in the rocks 

 of Tennessee, one of which is a common form : there is some obscurity 

 about its structure, though it probably appertains to this genus. The si- 

 milarity in form and general character of the smaller species of Stephano- 

 CRixus may have sometimes induced their reference to Haplocrinus, from 

 which they dilFer in the structure of the body and in the character of the 

 arms or tentacula. 



HAPLOCRINUS CLIO ( n. s.). 



Body very small, subangularly turbinate below the arm-openings, 

 pentangular when viewed from above, with protruding arm-bases. 

 Column-facet proportionally large, deeply impressed, the margin 

 -jj rounded. Basal plates five, very low. Three of the radial series 

 consist of two plates each, and two consist of but one plate each : 

 these latter are large, heptagonal, and rest directly upon the basal 

 plates. In the series of two, the first plate is small, quadrangular 

 in two rays and pentangular in one, all wider than high : the 

 second plate is intermediate in size between the first and the large 

 radials, quadrangular in two rays and pentangular in one. The 

 centres of the five large radial plates are strongly protruding at 

 the upper margins for the articulation of the arms, and show a 

 foramen with a central septum passing into the interior cavity of 



I 



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