TAXOCRINIDAE 387 



node on each axillary. iBr spaces wide, chiefly filled with strong perisome. 

 Anal tube large and prominent. Surface smooth. Crown of mature specimen, 

 41 mm. high ; 22 wide; base, 6 mm. 



IBB low but showing well above the column. BB fairly large, with acute 

 angles. Post. B extremely large and broad with very wide concave socket, sup- 

 porting a large anal tube with lower plates large, as wide as high, becoming 

 shorter above, and bordered on both sides with wide areas of very strong 

 perisome. RR and IBr of similar form and size, almost as long as -wide. IBr 3, 

 exceptionally 2; IIBr usually 4, sometimes 5, nearly as wide as IBr. IIIBr 6 

 on inner and about 8 in outer division. iBr 1 to 3, and small illlBr sometimes 

 present, followed by extensive perisome. Column unknown. 1 



The brachials throughout in this species are much longer than is usual for the genus, 

 and the development of anal structures and perisome much more profuse than in any other 

 Devonian species, recalling those of the later Subcarboniferous. In arm structure it super- 

 ficially resembles T. kclloggi, but it has a much narrower and more conical calyx, and is very 

 different in other details. The type specimen is in poor condition, and does not show the 

 structures plainly ; it seems, however, to have but two IBr in part of the rays, whereas the 

 other two extremely well-marked specimens have three consistently throughout. One of 

 these (fig. 10) shows all the characters of the species most beautifully ; and the other (fig. 11), 

 though not so perfect, fully confirms it. The latter has a Gasteropod commensally attached 

 over the anus. 



Types. Hall's original (fig. 9) is in the American Museum of Natural History, New 

 York; that of figure 10 in the New York State Museum, Albany; and that of figures 11a, b 

 is in the author's collection. 



Horizon and locality. Middle Devonian, Moscow shales of the Hamilton group ; 

 Canandaigua Lake, New York. 



Taxocrinus communis (Hall) 

 Plate LII, figs. 1-4 



Forbesiocrinus communis Hall, 17th Rep. New York St. Cab. Nat. Hist., 1863, p. 6 (Separate) ; Final 



Report, 1864, p. 55. — Hall and Whitfield, Geol. Surv. Ohio, II, Pal., 1875, p. 169, pi. 12, fig. 3, not 



figs. 4, 5. 

 Taxocrinus communis, Meek and Worthen, Proc. Acad. Nat. Sci. Philadelphia, IX, 1865, pp. 140, 141; 



Geol. Surv. Illinois, II, 1866, p. 270. — Wachsmuth and Springer, Revision Palaeocrinoidea, pt. 1, 



1879, p. 48. 



A small species, with elongate crown, and a very peculiar stem ; height to 

 width at second axillary, 1.4 to 1. Calyx greatly expanding, obconical below, 

 with narrow base and concave sides; height to width at I Ax, 1 to 1.4; spread 

 from base, 1 to 2.5. Arms heavy, rounded, tapering slowly, with not over three 

 bifurcations before infolding; iBr few, spaces narrow and elongate. Surface 

 smooth. 



IBB low, visible as a short ring. BB small, fairly acute-angled. RR and 

 IBr of similar form, about half as long as wide, increasing in width to the 

 axillary. IBr 3; IIBr 4 or 5, of about equal size, with one more division on 

 inner ramus at about 9th brachial in mature specimens, but not in younger. 



1 See explanation of Plate LII, figs. 9-1 1. 



