THE CRINOIDEA 



173 



Dr. 



them. Bactrocrinus, Schnur in Steininger (1849), Devonian, Eifel ; usu- 

 ally made a synonym of Homocrinus, but separated by Zittel (1879), Bather 

 (1893), and Jaekel (1895) ; differs from Palaeocrinus only in the occa- 

 sionally wider radial facet and rather more de- 

 veloped anal tube, in which points it approaches 

 Homocrinus. FAMILY 3. EUSPIROCRINIDAE. 

 Cyathocrinoidea with anal x hexagonal or 

 heptagonal, resting on post. B, but rising 

 above level of RR ; with RA pentagonal, 

 resting on post, and r. post. BB, supporting 

 x on one side, r. post. Rs on the other, and 

 a plate of the anal tube (rt) sunk into the 

 cup between them ; anus at end of a massive 

 anal tube ; post. O a madreporite ; arms 

 dichotomous, axial canal not separate from ven- 

 tral groove. Genera Euspirocrinus, Angelin 

 (1878; see Bather, 1893), Ordovician of 

 Canada, Silurian of Gotland (Figs. LXXXVII. 

 and XXXVIII.). The usual text-book figure 

 of E. spiralis is reversed. Closterocrinus, Hall 

 (1852), and Ampheristocrinus, Hall (1882), 

 both Silurian, N. America ; 3 IBB ; imper- 

 fectly known (Fig. LXXXVIIL). The anal 

 area of the family resembles that of the 

 advanced Dendrocrinoidea. FAMILY 4. SPHAE- 

 ROCRLNIDAE. Cyathocrinoidea, with 3 anal 

 plates as in Euspirocrinus, but differing in 

 that RA is comparatively large, x not rising. 



St - 



FIG. LXXXVI. 



Porocrinus'Smithi. 1, partial 

 reconstruction, seen from right 

 posterior radius, the arm of 



above RR, rt small and not, or hardly at all, ? 53TSS So^ 



rising above RR ; post. O a madreporite ; (Based on specimens belonging 



. , '.*, , . T> to Dr. G. J. Hinde.) x 2 



arms isotomous ; axial canal separate in r>r ,jj a , n . o, optical section across 



and R. Genera Sphaerocrinus, C. F. Roemer ?. brachiai (Br), showing rela- 



' tions of covering -plates (c.p). 



(1851; for history see Bather, 1892; for x 4 diam. other lettering as 

 structure, Jaekel, 1895), Devonian, Germany usual - 

 and England ; the anus pierces the tegmen directly through a ring 

 of small plates. Parisocrinus, W. & Sp. (1879), Devonian of Ger- 

 many, Carboniferous of England and N. America (Fig. XXVI. 6), has a 

 well-developed anal tube of hexagonal plates, which are folded at the edges. 





FIG. LXXXVIII. 

 Analysis of cup of Ampheristocrinus. 



FIG. LXXXVII. 

 Analysis of cup of Euspirocrinus spirtdis, 



FAMILY 5. CYATHOCRINIDAE. Cyathocrinoidea, with no anal except x, 

 which is in line with RR, and usually supports a large tube ; post. O a 

 madreporite ; arms isotomous, axial canal separate or not. Genera 

 Cyathocrinus, Miller (1821 ; see Bather, 1892-93, for full revision and 



