786 THE CRINOIDEA CAMEEATA OF NORTH AilERICA. 



Talarocrinus symmetricus Cass, and Ltox. 

 Plate LXXVIII. Figs. 4a, h, and 5. 



1860. Dichocrinus symmetricus — Casseday and Lyon; Proceed. Amer. Acad. Arts aud Sci., Vol. V., p. 21. 



1866. Dichocrinus symmetricus — Shumaed; Catal. Pateoz. Toss. N. Amer., p. 367. 



1877. Diohocriims symmetricus — S. A. Millee; Catal. Pala;oz. Foss. Amer. (1st Edit.), p. 76. 



1881. Talarocrinus symmetricus — W. and Sr. ; Revision Pala?ocr., Part 11., p. 87. 



1883. Talarocrinus symmetricus — S. A. Miller; Catal. Pal. Foss. Amer. (2d Edit.), p. 288. 



Syn. Dichocrinus degans — Lyon and Cass.; Proceed. Amer. Acad. Arts and Sci., Vol. T., p. 22. 



Sjn. Talarocrinus eler/ans — W. and Sp. ; Revision Palseocr., Part IL, p. 87. 



This species is closely allied to the preceding one, but somewhat smaller ; 

 the dorsal cup is more depressed, the form of the ventral disk more conical, 

 less contracted at the periphery, and the anal area wider. Dorsal cup semi- 

 globose, slightly lobed as seen from above or below, tlie plates without 

 ornamentation ; suture lines distinctly grooved. 



Basal cup quite shallow, widest at right angles to the interbasal suture. 

 Eadials spreading rapidly to the middle, less rapidly in the upper portions ; 

 the superior faces a little excavated, and their outer edges slightly truncated. 

 Anal plate longer than the radials, widest in the middle, the upper end 

 inflected, making the lateral faces convex. Costals and distichals very small; 

 not exposed upon the surface ; they are hidden by the two inner palmars of 

 the first row, which overlap them. The two outer palmars of the first row 

 rest upon the radials, their lateral faces support an interbrachial, which 

 also slightly touches the radials. Palmars four in the calyx, in contact later- 

 ally, short and rather deeply excavated for the reception of the higher 

 brachials, which are not preserved in the specimens. The arms of the same 

 ray are equidistant, while those of different rays are farther apart and sepa- 

 rated by a shallow groove. Ventral disk higher than the dorsal cup. The 

 interambulacral spaces filled by one and two narrow plates followed by the 

 orals ; the first radial dome plate is conical. The large anal plate supports 

 three plates, of which the middle one is considerably wider than high and 

 somewhat depressed, the two others quite narrow. The second row also con- 

 sists of three pieces, and these are succeeded by numerous smaller ones, 

 which form an elongate rounded ridge containing the anus. This ridge, 

 which is bounded laterally by a shallow groove, extends to the posterior oral 

 in an almost vertical line. The primary radial dome plates alternate with 

 the orals ; they are large and either spinous or strongly tuberculous. The 

 secondary radial dome plates are elongate and enclose a large interdistichal. 



