286 TWENTIETH REPORT ON THE STATE CABINET. 



*' pi. ix, f. 3 <z), but is smaller, and has more slender rays, with more angu-* 

 * lar spaces between them. It also differs in having but two ranges of plates 



** on each side of the ambulacral grooves on the under side, instead of 

 ' three." 

 The fact of having two ranges of plates only on the lower side must 



separate this species from Petraster of Billings, since the presence of 



a partial intermediate range, or "a few disc-plates" on the ventral side 



form an essential feature of that genus. 



Geological formation and locality. In Lower Silurian strata of the age 



of the Trenton or Hudson-river group, at Oswego, Kendall county, Illinois. 



« 



Pal^aster antiquata. 



PLATE 



jlsterias antiquata : Locke, Proceed. Acad. Nat. Scien. Philadelphia, Vol, iii, p. 32 



(with wood cut). 1846. 



This species was noticed by Dr. Locke, as cited above, but without spe- 

 cific description, and expressing a doubt whether it was or was not identical 

 with the Asterias antiqua of Troost. The figure would indicate a distinct 

 species from that of Dr. Troost ; and if we can judge from the illustra- 

 tion, it is not a Palasterina. The question may not be determined, 

 however, without reference to the original specimen. 



In the figure of Dr. Locke, there are two ranges, and in some places 

 three ranges of plates, represented as bordering the ambulacral groove. 



Geological formation and locality. The specimen is from the shales of 

 the age of the Hudson-river group, near Cincinnati, Ohio. 



PALiEASTER JAMESI. 



Fossil .Asterias : Report of G. Graham, J. G. Anthony and TJ. P. James. "Western 

 Acad, of Nat. Sciences, American Journal of Science (n.s.), Vol. i, no. 3, 



p. 441. 1841. 



jlsterias anthonii : Dana, Manual of Geology, p. 221, with figure. 1863. 



Palasterina [.?] jamesii : Dana, Amer. Jour. Science (n. s.), Vol. xxxv, p. 295 



This species, if we may judge from the figure given, is not a Palas- 

 terina, as it wants the ^^ plated disc which fills up the angles"* an essen- 

 tial character of the genus. 



In the figure in the American Journal of Science, the plates of some of 

 the rays are shown as extending from the ambulacral groove to the margin ; 

 while in others they are shown as divided, giving a marginal and adambu- 

 lacral range, as in Paljeaster ; and in the absence of disc-plates, I can 

 see no other reference for the species but to that genus. 



Geological formation and locality. This species occurs in shales of the 

 age of the Hudson-river group, at Cincinnati. 



• Salter, Annals and Mag. Nat. History, Nov. 1857; cited by Billings, Decade iii. 

 p. 76. 1858. 



