A NEW AMERICAN JURASSIC CRINOID. 



By Frank SriiiNCEK, 

 Of East Las Vegas, New Mexico. 



The first specimen of a fossil species of Pentacrinidse from Ameri- 

 can rocks was described by Meek and Hayden in 1S58," under the 

 name Pentacrinites asferiscus, from some isolated stem joints found 

 in the Jurassic near the southwest base of the Black Hills of Dakota. 

 They afterwards redescribed and figured the species in their work 

 on the Paleontology of the Upper Missouri.'' Their figures on 

 Plate 3 were based upon the original specimen; but on page 67 

 the authors gave a text figure, not very accurate, of some stem frag- 

 ments with cirri attached, which they referred with doubt to their 

 species. This specimen, according to the label in the U. S. National 

 Museum, came from Red Buttes, Nebraska, a locality now included 

 in the State of Wyoming. The description was stated by the authors 

 to apply " more particularly to the largest sized specimens," which 

 came from a different locality, and which, as represented by the 

 figures on Plate 3, were considered by Dr. P. H. Carpenter " to 

 belong to the genus ^^ Extracrinus'''' (Pentacrmus, sensu str.), al- 

 though he perhaps based his opinion rather upon the figures given 

 by White '^ of a specimen from Utah than upon those of Meek and 

 Hayden. So far as can be judged from a few isolated joints, there 

 is reasonable ground to l)elieve that the doubt expressed by the 

 authors as to the specific identity of the two specimens is well 

 founded; those of the typical form are nearly twice as large as the 

 others, and the petaloid sectors on the articular face are more sharply 

 angular. The transverse view given in the text figure on page 67 

 of the work cited is not correct, the structure being rather poorly 



« Proc. Acad. Nat. Sci. Philadelphia, X,' p. 49; XII, 1860, p. 410. 

 * Smithsonian Contributions to Knowledge, No. 172, 1865, p. 67, pi. iii, figs. 

 2 a, &. 



^ Challenger Report, Stalked Crinoids, pp. 143, 297. 



<* Wheeler, Geol. & Geog. Surv., IV, p. 162, pi. xtii, fig. 6 a. 



Proceedinos U. S. National Museum- Vol. XXXVl— No. 1 664. 



179 



