360 SMITHSONIAN INSTITUTION 



nearly filling the area, but not suturally connected at left side, and probably 

 not at the right. iBr small and narrow, sometimes not appearing externally. 

 Column unknown. 



This species departs from the characters of the genus in its heterotomous arms. Their 

 arrangement is really not very different in principle from that of a great many species which 

 we call dichotomous, in which the outer ramus of the dichotom is slightly the larger, and has 

 longer intervals between bifurcations. Here this has gone so far in the direction of heter- 

 otomy such as we have in Dactylocrinus that the species might be separated generically on 

 that account. It will not go under Dactylocrinus or its allies by reason of the characters of 

 the anal tube and base, and I have preferred to consider it as an early variant of the present 

 genus, of which it is the only Silurian representative. T. rigens is clearly a synonym. In 

 addition to Angelin's two types which are refigured (PI. XLVIII, figs. 1, 2), there are two 

 other specimens showing the anal side, both from Wisby. In some of these there is a curious 

 open space between the infrabasals marked by a distinct notch at the exterior (PI. XLVIII, 

 figs. 2b, 4). 



Types. Riks Museum, Stockholm, Sweden. 



Horizon and locality. Silurian, Wenlock limestone ; Faro and Wisby, Island of 

 Gotland. 



Eutaxocrinus rhenanus (C. F. Roemer) 



Plate XLVIII, figs. 5-10 



Cyathocrinus rhenanus Roemer, Foss. Fauna Dev. Geb. Rhein., 1851, p. 7, pi. 2, figs. 2a-e; Verh. Nat. Hist. 



Ver. preus. Rheinl., VIII, 1851, p. 363, pi. 8, figs. 2a-e. — Miiller, Abhandl. Akad. Wiss. Berlin, 1857, 



P- 245. 

 Taxocrinus rhenanus, Sandberger and Sandberger, Verst. Rhein. Schicht. Nassau, 1850-56, p. 393, pi. 35, 



with text-fig., figs. 17, 17a, not 17b, c. {Cyathocrinus on the plate). — Miiller, Monatsber., March 



1858, p. 185. — Beyrich, Monatsber. Akad. Wiss. Berlin, 1871, p. 43 (Transl. in Ann. and Mag. Nat. 



Hist., (4) VII, p. 401). — Wachsmuth and Springer, Revision Palaeocrinoidea, pt. I, 1879, p. 49. — ■ 



Follmann, Verh. Naturh. Verein, 1882, p. 164 (Unterdev. Schicht. Olkenbach, pp. 36, 38) ; Unterdev. 



Crinoiden, 1887, p. 4. 

 Cyathocrinus brachydactylus F. A. Roemer, Palaeontographica XIII, 1866, p. 205, pi. 35, figs. 10a, b. 



A medium-sized species. Crown elongate, with broad base, expanding 

 gradually from the base to about the third bifurcation; widest about the ITIBr, 

 where height to width is about 1.4 to 1 ; of calyx at top of IBr, 1 to 1.5 ; spread 

 from base, 1 to 1.8. iBr wanting or small and narrow. Anal structures un- 

 known. Arms strong, rounded, diminishing by nearly half at each bifurcation, 

 and lying close together though not abutting; sutures obscurely arcuate. Sur- 

 face throughout ornamented with fine tubercles, most prominent on the sides of 

 the arms ; on the stem they take the form of crenulation at the edge of the 

 columnals. Dimensions of type specimen: Crown, 33 mm. high by about 23 

 wide ; base, 9 mm. 



IBB low, but little visible beyond the column. BB short and wide, with 

 rather obtuse salient angles. Anal side unknown. RR and IBr large, of similar 

 shape, gradually widening upward leaving little space for iBr, which if present 

 must be narrow and elongate. IIBr 4. IIIBr 7 or 8 in the outer divisions, and 

 5 in the inner. Arms infolding shortly above the third bifurcation. Column 

 robust, commencing flush with the base with very thin columnals, strongly 



