310 SMITHSONIAN INSTITUTION 



A well-marked and constant species, nearer to D. excavatus than to any other, but with- 

 out its deep basal cavity ; otherwise distinguished by its longer, more rounded, and less taper- 

 ing ray divisions. In that species the ramules become equal to the main branches at about 

 the third division, whereas here they are well differentiated to at least the sixth. 



Types. The originals of figures 7 and 8 are in the collection of Professor R. R. Rowley, 

 of Louisiana, Missouri ; that of figure 9 is in the author's collection. 



Horizon and locality. Middle Devonian, Hamilton Group, limestone bed at middle of 

 Craghead Creek shale; near Fulton, Callaway County, Missouri, associated with three 

 described species of Melocrinus. 



Dactylocrinus oligoptilus (Pacht) 

 Plate XLI, figs. 1-2 



Dimerocrinites oligoptilus Pacht, Beitr. Kenntn. Dimerocr., (Separate) 1852, p. 8, pi. 1, figs. 1-9; pi. 2, 



figs. 1-12; pi. 3, figs. 1-12 [Verh. K. Russ. Gesell., 1853, p. 339]. 

 Dimerocrinus oligoptilus, Eichwald, Lethaea Rossica, I, i860, p. 597. — Wachsmuth and Springer, Revision 



Palaeocrinoidea, pt. 2, 1881, p. 231. 

 Dactylocrinus oligoptilus, Quenstedt, Petref. Deutschlands, IV, 1876, p. 520, pi. 108, fig. 32 {Dimerocrinus 



on plate). — Jaekel, Zeitschr. d. deutsch. geol. Gesell., XLIX, for 1897 [1898], p. 44. 

 Dimerocrinus {Taxocrinus ?) oligoptilus,. Wenjukoff, Fauna Dev. Syst. Nordw. u. Cent. Russ., 1886, 



Original, pp. 447, 691 (Resume, p. 31), pi. I, fig. 11. 

 Taxocrinus oligoptilus, Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 3, 1886, p. 144. 



Type of the genus. 



Specimens attaining a large size. Crown elongate, expanding gradually 

 until above the second bifurcation, rays increasing- in width above the radials. 

 Height to width at IIBr 3 , 1 to 1.4; spread of calyx, 1 to 3.2; cross-section at that 

 level decagonal, side outline slightly curved. Base broad, expanding into a 

 slightly rounded rim and then recurving into a shallow concavity, formed by 

 the incurved parts of radials and basals, with the column facet at the bottom. 

 Surface coarsely granulose. Crown of maximum specimen 52 mm. high by 32 

 wide; base at outside of rim 10 mm. ; diameter of column at base 5 mm. 



IBB small, entirely covered by proximal columnals at bottom of concavity. 

 BB much elongated, projecting in narrow tongues which curve over the rim of 

 the concavity; post. B much higher, reaching to about the top level of RR, where 

 it is truncate and narrow, partly supporting first anal plate. Anal x of moderate 

 size, with three lower faces supported by post. B and short shoulders of RR; 

 it is about the height of the abutting IBr, angular above, followed by a median 

 series of several plates (somewhat disturbed in the type specimen), with some 

 smaller plates at either side, all suturally united to adjacent rays and narrowing 

 to a point as the rays meet above. iBr one large plate, more than twice the size of 

 anal x, acute-angled above; illBr sometimes present. RR with tongue-like pro- 

 jection curving into the basal concavity between BB; primibrachs half as high 

 as wide, and about the same size as RR, but slightly narrower on account of the 

 interbrachials; above them the rays increase in width rapidly. Rays and their 

 divisions rounded, tapering rapidly ; the two rami equal in size, the outer mar- 

 gins of the ramuliferous dichotoms contiguous but not interlocking. IIBr 3, 



