310 PROCEEDINGS OF THE ACADEMY OF [1881. 



Apical dome plates well defined but somewhat displaced, owing 

 to the great number of plates which surround the anus. Radial 

 regions of the dome prominent, in form of five high ridges which 

 bifurcate, sending a branch to each arm. They are composed of 

 two rows of rather large convex and elongate plates, transversely 

 arranged, which in branching sepai^ate, and pass on as two single 

 rows of plates. 



Interradial dome regions depressed, and composed of small 

 irregular pieces. 



Column round ; central canal of medium size. 



Geological Position, etc. — Glyptaster is known onl^- from the 

 Niagara group, Upper Silurian, of America. 



We recognize the following species : — 



*1861 (?). Glyptaster armosus McChcsney. (Eucalyptocr armosus) Desc. New Pal. 



Crin., p. 95 : also 1867, Glyptocr. (1) armosus, ChicHgo Acad. Sci., p. 23, PI. 



7, fig. 6; Hall, 20th Rep. N. Y. St. Cab. Nat, Hist., PI. 10, fig. 11. Niagara 



limest. Racine, Wis. 

 Sj/n. Glytocr. siphonatus Hall. (Not.) 1861, Geol. Rep. Wis., p. 22 ; 20th 



Rep. N. Y. Bt. Cab. Nat. Wst., p. 328, PI. 10. fig. 11. 

 Gl armosus was described from internal casts, and there is some doubt as to 



its specific and even generic character. 

 1852. Glyptaster brachiatus Hall. Type of the genus. Paleont. N. Y., ii, p. 187, 



PI. 41, fig. 4. Niagara gr. Lockport, N. Y. 

 1863. Glyptafter inornatus Hnll. Trans. Alb. Inst., iv, p. 205 : also 28t>i R.p. N. Y. 



St. Cab. Nat. Hist., 1879 (ed. ii), p. 134, PI. 14, figs. 1-6. Niagara gr. 



Waldron, Ind. 

 1863. Glyptaster occidentalis Hall. Trans. Alb. Inst., iv, p. 204; al.-'o 20th Rep. 



N. Y. St. Cab. Nat. Hist., p. 305, and 28th Rep. 1879 (ed. ii), PI. 18, figs. 



7, 11. Niagara gr. Waldron, Ind., and Racine, Wis. 

 1804. (?) Glyptaster pentangularis Hall. 20th Rep. N. Y. St. Cab. Na^. Hist., p. 



326, PI. 10, fig. 3 (advance sheets 1864). Niagara gr. Rueine, Wis. 

 The species was described from casts, but probably belongs to this genus. 



Subgenus EUCRINTJS Angelin. 



1878. Angelin. Iconogr. Crin. Suec, p. 24. 



1879. Zittel. Handb. der Palaeont., i, p. 375. 



Syn. BJiodocrinus Schultze 1866 (in part). Echin. Eifl. Kalk, p. 57. 

 Syn. Dimerocrinus (in part) Phillips, 1839 ; d'Orbigny, 1850 and 

 1853 ; Pictet, 1857. 



Eucrinus agrees with Glyptaster in the form of the calj^x, the 

 style of ornamentation, and size and form of underbasals. It 

 also has 3X5 primary radials, and an elevated ridge all along the 

 radial regions, but diff^^ers in having tertiary radials — from one to 

 two or more— and four arms to each ray. There is no departure 



