THE FOSSIL CEINOID GENUS DOLATOCRINUS AND ITS ALLIES. 31 



The dorsal cup is relatively low, scarcely higher than the tegmen, 

 with a shallow concavity at the bottom leading to a small basal pit. 

 Plates low convex, with smooth surface, and a sharp, abruptly rising 

 median ridge (not well preserved in Wachsmuth and Springer's 

 specimen) upon the radial series extending to the arm bases. Tegmen 

 I'ather high, composed of large, smooth plates, wrth broad and shallow 

 interambulacral depressions. Arms 10. It is large-sized species, 

 typical specimens being about 24 mm. high, and 36 mm. wide, and 

 average height to width about 1 : 1.4. 



Horizon and localitij. — Onondaga limestone: Schoharie and else- 

 where in New York. 



DOLATOCRINUS MARSHI Lyon. 



Plate 5, fig. 14. 



Dolatocrinus marshi Lyon. Trans. Amer. Philos. Soc, vol. 13, 1869, p. 461, pi. 27, 

 figs, n, n', n.2— Miller and Gurley, Bull. 4, 111. St. Mus., 1894, p. 12, not pi. 1, 

 fig. 8=2). grandis. — Wachsmuth and Springer, N. A. Crin. Cam., 1897, p. 312, 

 pi. 26, figs, la-d.— Rowley in Greene, 1903, p. 159 (not pi. 47, figs. 7, S=D. 

 grandis). 



Of the type of D. speciosus, with a similar liigh, abruptly rising 

 radial ridge continuous to the arm bases, but with rather more angular 

 sides, higher tegmen having a few small scattering tubercles, and a 

 strong dorsal ornament by fine radiating striae. It is on an average 

 of smaller size, and height to width is about 1 : 1.3. The entire facies 

 of this form bears a strong resemblance to that of the New York 

 species, the figured specimen of whicli might conceivably be a much 

 eroded specimen of this. If a well-preserved New York specimen 

 showed distinct radiating striae upon the radial and interbrachial 

 plates, I should not know how to separate the species. The long 

 redescription and figure of this species by Miller and Gurley were 

 based upon a small specimen of D. grandis, and are erroneous and 

 misleading in every particular; Rowley followed their example, but 

 afterwards made a new species for his specimen. Those of Wachs- 

 muth and Springer were made from Lyon's very perfect type speci- 

 men, now in my possession. 



This species was for a long time extremely rare, but I obtained in 

 recent years a number of additional good specimens which confirm 

 the type, but indicate some variation in size by wa,}" of increase to a 

 maximum of 35 mm, high by 50 mm. wide, one-half larger than the 

 usual size. From these it is seen that secundibrachs to the number 

 of three are incorporated, followed b}' one or more biserial pairs, 

 producing four to six conspicuous pinnule openings to the inter- 

 brachial spaces, and giving an appearance at the arm bases analogous 

 to tliat of D. grandis, by which Miller and Gurley were probably 

 misled. 



Horizon and localitg .^OnondsigSi (Jeffersonville) limestone: Louis- 

 ville, Kentucky, and vicinity. 



