1886.] NATURAL SCIENCES OF PHILADELPHIA. 197 



one-balf narrower above than below, owing to an angular exten- 

 sion at the lower half of its two lateral faces, which fit closely 

 into the adjoining excavated side of the large radials. Similar 

 processes arise from the sides of the two smaller plates, but here 

 only along the suture toward the larger one, the opposite suture 

 being perfectly straight. B}^ means of the lateral extensions, the 

 large radials, which at their basi-radial suture have nearlj^ the 

 same width as the smaller ones, attain at their upper face three 

 times the width of the other plates. 



The articular surface of the radials is truncated, unusually 

 thick, and closely resembles that of Catillocrinus. Mycocrinus 

 boletus must have had fifteen arms, for there are fifteen rather 

 shallow ambulacral grooves, which pass from near the periphery 

 of the cal3^x to the radial centre. There are six upon each of the 

 two large radials, and one upon each of the two smaller ones. 

 The six grooves upon the two larger radials unite into one, and 

 hence there are but five main trunks entering the inner cavity. 

 The median part of every groove has a deep linear furrow, which 

 takes a somewhat downward course, and penetrates the walls of 

 the radials. Close to the peripliery, outside of each groove, there 

 is a well-marked slit-like axial canal, making fifteen in all, which 

 pierce the radials throughout their full length, and enter the upper 

 margins of the basals. These canals or tunneled passages are 

 evidently axial canals, which entered through the twelve slit-like 

 openings at the inner floor of the basals the chambered organ, 

 and as such communicated with the arms. 



The body cavity is very small, its width not equaling the thick- 

 ness of the radials ; its depth being less even than its width. 

 Form of the arms, construction of summit and anus unknown. 



The column seems to have been circular, with a small, round 

 central canal. The only species is : 



1866. Mycocrinus boletus Schultze, Monogr. Eehin. Eifl. Kalk., p. 222, PI. 7, fig. 4. 

 Stringocephalenkalk, Devonian. Nollenbach (Eifel), Germany. 



Family XXVI. CALCEOCRINID^ Meek aud W. 



1878. Meek and Worthen, Geol. Rep. Illinois, v, p. 443. 

 1883. De Loriol, Paleont. Franqaise, vi (Crinoides), p. 51. 



Syn. ChirocrinidcB, Angelin, 1878, Icon. Criu. Suec, p. 23. 



Syn. CheirocrinidcB, Zittel, 1879, Handb. d. Palaeont., i, p. 357. 



The only known genus of this family has been variously referred 

 to Cheirocrinus aud Calceocrinus. As early as 1851, Hall, in 



