PLATYCRmiDiE. 719 



Original type said to be in the White collection at Ann Arbor, Mich., but 

 not certainly identified. 



Remarks. — Our description was made from the quite perfect specimen 

 figured on Plate LXVI., Fig. 4, which we have identified as belonging to this 

 species, although much smaller than Hall's type, and the specimen figured 

 by Miller as the type of P. sulcatus. The specimen figured by Whitfield as 

 Hall's type is somewhat imperfect in the basal disk ; the very large pentapet- 

 alous opening in the centre is due to accident, as no Platycrinus in its 

 normal condition had an opening in the base for the central canal of any 

 such size or shape as the figure shows. The species is interesting as being 

 the first authentic Plati/crinus in America in which a long anal tube has 

 been observed. It is plainly shown in our specimen, but is broken off just 

 within the tips of the arms, and does not appear from the view given in 

 our figure. 



EUCLADOCRINUS Meek (emended W. and Sp.). 



1871. Meek; TJ. S. Geol. Survej of Montana by Hayden, p. 373. 



1878. W. and Sp. ; Proceed. Acad, Nat. Sci. Pliila., p. 3i3, and 1881, Revision, Part II., p. 76 (Proceed. 



Acad. Nat. Sci. Phila., p. 250). 

 1890. S. A. MiLLEK ; North Amer. Geol. and Pateont., p. 244. 

 Syn. Plati/crimis (in part) Hall 1858 ; White 1863. 



Construction of the dorsal cup, ventral disk and column, as in Platycrinvs, 

 but the brachials extended outward and forming large tubular appendages 

 or arm trunks, which pass out from the calyx, and give off the arms alter- 

 nately from opposite sides. These trunks are extensions of the calyx, com- 

 posed of a greater or less number of successive orders of brachials, of two 

 plates to each order; they are roofed over by large, rigid, or nearly rigid, 

 covering plates throughout their whole length, forming a good sized tubular 

 passage underneath, which communicates with the inner part of the calyx. 

 There are generally two such trunks to the ray, which are in contact to near 

 the top of the palmars, and support a single arm from every axillary. Some 

 species, however, have but one appendage to the ray, and their arms are 

 given ofi" in clusters of four or more from every second brachial. The arms 

 are of moderate size, biserial and pinnnle-bearing, but were apparently short, 

 and the lower ones did not rise to the top of the crown. 



Distribution. — Restricted, so far as known, to the upper part of the 

 Burlington and the lower beds of the Keokuk groups of America. 



Type of the genus : Eiieladocrinus montanensis Meek. 



