1881.] NATURAL SCIENCES OF PHILADKLPHIA. 36t 



median part, which probabl}' include the apical plates, somewhat 

 larger. Anal aperture directly through the vault, small, sub- 

 central. 



Column subpentagonal, its lateral faces but little depressed ; 

 central canal rather large. 



Geological Position^ etc. — Eeteocririus belongs to the age of the 

 Trenton and Hudson River groups, and is only found in America. 



We place here the following species : — 



■■■1872. Beteoorinus Baeri Meek. (Glyptocr. Baeri) Amer. Journ. Sci. and Arts, iii 



(Ser. 3), p. 260 ; also 1873, Geol. Rep. Ohio, Palaeont., p. 37, PI. 2, fig. 1 a, b. 



Upper part of Hudson Riv. gr. Richmond, Ind. 

 *1881. Eeteocrinus cognatus S. A. Miller. (Glyptocr. cognatus) Journ. Cincin. 



See. Nat. Hist. (April No.), p. 7, PI. 1, fig. 5. Hudson River gr. Middle- 



toirn, Ohio. 

 *1859. Beteocr. fimbriatus Billings. Geol. Rep. Canada, Decade iv, p. 65, PI. 9, 



figs. 3 a, b, c. Hudson River gr. Island of Anticosti. 

 *1881. Beteocr. gracilis Wetherby. (Glyptocr. gracilis) Now in press. Cincin. 



Journ. Nat. Hist., PI. ii, figs. 2, 2 a. Hudson River gr. 

 «1866. Beteocr. O'Nealli Hall. Proposed type of the genus. (Glyptocr. O'Nealli) 



Desc. New Sp. Crin., p. 2 ; also 24th Rep. N. Y. St. Cab. Nat. Hist., p. 206, 



PI. 5, figs. 18, 19; Meek, 1873, Geol. Rep. Ohio, Paleont., i, p. 34, PI. 2, figs. 



3 a, b, c. Upper part of the Hudson River gr. Lebanon, 0. 



*1880. Beteocr. Bichardsoni Wetherby. (Glptocr. Bichardsoni) Journ. Cincin. 



Soc. Nat. Hist; Desc. New Crin. Cincin. gr., PI. 16, figs. 1 a-e. Hudson 



River gr. Clinton Co., Ohio. 

 *1859. Beteocr. stellaris Billings. Geol. Rep. Canada Dec, iv, p. 64, PI. 9, figs. 



4 a-e. Trenton limestone. Ottawa, Can. 



h. Glyptasterites. 

 4. GLYPTASTEB Hall. 



1852. Hall. Paleont. N. York, ii, p. 187. 



1863. Hall. Trans. Albany Inst., iv, p. 203. 



1879. Hall. 28th Rep. N. Y. St. Cab. Nat. Hist. (ed. ii), p. 133. 



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



The genus Glyptaster is involved in some confusion. It was 

 founded upon a specimen from the Niagara group of New York, 

 which Hall named Glyptaster hrachiatus. In the type specimen, 

 the plates of the calyx are altogether obscure except possibly the 

 basals, which were stated to be five in number. The specimen 

 further showed five highly elevated ridges along the radial por- 

 tions of the calyx, and ten long, slender arms, which are com- 

 posed of a double series of interlocking joints, and spread out 



