180 PROCEEniNGS OF THE NATIONAL MU8EUM. vol. xxxvi. 



defined in the specimen. The Red Buttes specimen shows a rather 

 obtusely pentanguLar, smooth stem, with straight sides, having 

 eleven or twelve joints to the internode, and cirri tapering rapidly 

 near the proximal end. 



Separate stem joints, more or less similar to both of Meek and Hay- 

 den 's figures, have since been collected by the staif of the U. S. Geolog- 

 ical Survey in various localities throughout the Rocky Mountain and 

 Pacific regions, but no vestige of the crown was obtained until 1899, 

 when the late Prof. W. C. Knight, of the University of Wyoming, in 

 the course of some investigations among the famous Dinosaur beds 

 near Medicine Bow, Wyoming, discovered some small slabs of lime- 

 stone containing numerous stems and fragments of arms, with one 

 very complete crown. This he reported as Pentacrinus asteriscus.'^ 

 In the following year Mr. H. T. Martin, of the University of Kansas, 

 visited the Medicine Boav locality and succeeded in finding a few 

 more pieces of the rock containing the crinoid remains, which by 

 careful cleaning have yielded some additional specimens useful for 

 description. Through the obliging courtesy of these gentlemen this 

 material was placed in my hands, but pressure of other matters has 

 prevented the preparation of the necessary figures for their descrip- 

 tion until now. 



The locality of these fossils is in the same region and horizon as 

 Meek and Hayden's Red Buttes sjjecimens, and they probably belong 

 to the same species. Assuming, for the reasons already given, that 

 they are not included in the typical Pentacrinites asteriscus — of which 

 in any event we know nothing beyond the form and size of separate 

 stem joints — it seeuis proper to describe this form as a new species. 

 I therefore propose to associate with it the name of the lamented 

 geologist to whose researches we are indebted for its discovery. 



ISOCRINUS KNIGHTI, new species. 



1865. ? PentavriuUcs nstvrhviix Meek and IIayuen, Pal. Upper Missouri, 

 p. 67, text fifi. (not pi. iii, fifis. 2 a. h.) 



Specimens of moderate size. 



Stem smooth, long, slightly increasing in diameter distally; pen- 

 tagonal with straight sides, except at the proximal end, where for the 

 first few immature internodes the younger joints are stellate. Inter- 

 nodals about 14, but varying from 12 to 17 in the mature parts; dis- 

 tinctly crenulated at the margins; nodals not enlarged, scarcely dis- 

 tinguishable from the others except b}^ the cirrus sockets; these are 

 rather shallow, not extending to the hypozygal, or infranodal joint, 

 but usually encroaching upon the supranodal, in which case the 

 apposed faces of these two joints are more or less indented, producing 



*" Jurassic Rocks of Southwesteru AVyoiuiug. Bull. Geol. Soc. America, XI, 

 p. 377. 



