TKENTON LIMESTONE. 91 



128. 2. ASTERIAS MATUTINA (n. .9/j.). 



Pu XXIX. Figs. 5 a, b. 



Body small, wiili five radiating aims; arms elongated (length twice and a half the 

 width of the body), terete, acute, composed of three rows of plates, which join above by 

 their lateral margins. Beneath each upper lateral row of plates there is an inferior lateral 

 range visilile, leaving the sulcus beneath the middle row, which is often depressed. The 

 dorsal plates are somewhat hexagonal ; those of the arms quadrangular : surface punctate 

 or granulate, perhaps from tlie removal of the spines covering the surfiicc. 



The .specimen is considerably cruslied, and two of the arms broken off at the base ; the 

 madreporiform tubercle upon the back is not visilile in our specimen. From its condition, 

 the structure cannot be entirely made out, but it is sufficiently clear to enable any one to 

 recognize the species. 



Three specimens of this highly interesting species are known to me, two of wliich occur 

 in the Trenton limestone of New-York. It ])ears some resemblance to the one found at 

 Cincinnati ; but it would appear, from the figure and description of Prof. Locke ( Pro- 

 ceedings Acad. JVat. Sci., Vol. iii. p. 33 ), that it is a distinct species, being at least twice 

 as large, with the centre proportionally larger, and the plates composing the arms smaller 

 than in our species. 



The name {Jlsta-ias antiqua) given by Prof. Locke, i.s already appropriated by Troost 

 for a very distinct species, judging from his figure (Trans. Geol. Soc. Pcnn., Vol. i. p. 232, 

 pi. 10, fig. 9 ) , and probabl}- holding a higher geological position. Prof. Troost also 

 mentions ( page 235 of the work just cited ) having " found five other species of free 

 AsTERiTES : one of them occurring in a lower stratum than that in wliich the Jl. antiqua 

 is imbedded, and the four others in a higher situation ; all, nevertheless, below the Coal." 

 It is therefore quite certain that the Genus Asterias existed during the deposition of the 

 older Silurian rocks in localities widely separated from each other, and also that the genus 

 is represented I)y more than a single species. 



Fig. 5 a. The specimen, natural size. 



Fig. 5 A. A portion enlarged, showing the form of the plates and the punctate surface. 



Position and locality. The specimen figured is from the thin shelly layers at Trenton 

 falls, about midway of the rock. Another specimen has been found near Canajoharic, 

 probably from a lower position in the Trenton limestone. An imperfect specimen, ap- 

 parently of the same species, has been found in the shales of the Hudson-river group, by 

 Gen, Spinner, of Mohaw'k. (Collection of W. H. Pbase.) 



12* 



