THE CRINOIDEA 



173 



Or 



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 (r) 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- 

 ROCRINIDAE. Cyathocrinoidea, with 3 anal 



plates as in Empirocrinus but differing in reconstructioil) seen from right 

 that RA is comparatively large, x not rising posterior radius, the arm of 

 above RR, rt small and not, or hardly at all, " tTSi SS2 

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

 arms isotomous ; axial canal separate in Br j ai r - 2?opUcai^ection across 

 and R. Genera Spliaerocrinus, C. F. Roemer a . brachiai (Br), showing reia- 



' 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. 



Sf- 



Fio. LXXXV1. 

 Porocrinus Smithi. 1, partial 



Fio. LXXXVII. FIG. LXXXVIIL 



Analysis of cup of Euspirocrinus sidrcdis. Analysis of cup of Amplieristocrintis. 



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

 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 



