DESCRIPTIONS OF SOME NEW lU.ASTOIDS. 93 



they occupy only five-sixths of that length. It differsTrom E. Vertieu- 

 illi in being a much smaller species, and in the entirely different orna- 

 mentation; from Ehracri/iits an}:;iilaris F.yon, E. lucina Hall, and our 

 E. ol>07'aii/s, as lacking that marked angularity of the body so conspic- 

 uous in each of these species. There is a general resemblance to the 

 figure given by Montgomery of Nucleocrinus Canadensis, but no direct 

 comparison can be made, as his paper deals in generic rather than 

 specific descriptions. The only specific characteristic clearly brought 

 out, "the prominently arched radials," are totally inapplicable to our 

 species. 



Geological position, etc.: In the shales of the Hamilton group, Buf- 

 falo, Iowa, and at the top of the same group in the Thunder Bay region 

 of Northern Michigan. The type specimens are in the cabinet of the 

 writer. 



PENTREMITIDEA'^ D'Orp.ignv. 



1849. D'Orljigiiy, Prodrome de Palceoiit., p. 102. 



1853. D'()rl)igny, Cours Elementaire, p. 139. 



1882. Etheridge and Carjienter, Ann. and Mag. Nat. Hist., p. 220. 



Pentremitidea AMERICANA Barris, Nov. Sp. 



Plate I. — Fit; . 4. Pcntrcmiticlca aniericana. 



Body small iiyriform, height twice the greatest width, which is across 

 the radial lijts. Dorsal side in form of a cone with slightly convex 

 sides, triangular at the end, but gradually assuming a strongly marked 

 pentalobate aspect; ventral side of the body ecjual in length to the 

 dorsal side, curving gently in an upward direction; broadly truncate 

 and somewhat depressed at the oro-anal regions. 



Basals forming a triangular vase, with rounded angles, and of a height 

 greater than the width at the top, upper edges slightly concave. 



Radials two-thirds the length of the body, a little more sloping than 

 the basals; width at basi-radial suture ecjual to the width of the plates 

 at the opposite side. The forks occupy two-thirds the length of the 

 plates, are comparatively narrow, and end in a sharp point which con- 



*Theo;^cnus Peiitremilidca dilTcrs fioin Trooxlocrinns Shumard, its nearest allied form, in 

 having^ quite inconspicuous interradial plates, always placed within the truncate upper face of 

 the body, and only five spiracles, which are strictly interradial, while in TrooxlocHntis the inter- 

 radials are always visible in a side view of the specimen, and there are ten slit-like spiracles 

 alonof the lateral ed^e of the ambulacra," and a separate anal opening-. I am indebted to Mr. 

 Wachsmuth for the recognition of the .above species as Pentremitidea, and who claims that it is 

 the first one that has been discovered in America. 



