REVISION OF PALEOZOIC STELLEROIDEA. 57 



In the Lower Carboniferous genus Neopdlseaster the prmiitive 

 disk structure of Hudsonaster is also retained in its essential fea- 

 tures. Otherwise these genera arc easily distinguished, as is pointed 

 out in the remarks on Neopalseaster. 



HUDSONASTER MATUTINUS (Hall). 

 Plate 2, fig. 2; plate 3, fig. 2; plate 5, figs. 1, 2. 



Asterias matutina Hai.l, Nat. Hist. N. Y., Pal., vol. 1, 1S47, p. 91, pi. 29, figs. 



5a, 56. 

 Palxaster matiitinus Hall, Twentieth Rep. N. Y. State Cab. Nat. Hist., 1868, 



p. 283, pi. 9, fig. 2; rev. ed., 1868=1870, p. 325, pi. 9, fig. 2. 

 Petrastcr rigidus (part) Billings, Geol. Surv. Canada, Can. Org. Rem., dec. 3, 



1858, pi. 10, fig. 36 (not fig. 3a).— Hall, Twentieth Rep. N. Y. State Cab. 



Nat. Hist.,1868, p. 294; rev. ed., 1868=1870, p. 337. 



Original description. — "Body small, with five radiating arms, 

 arms elongated (length twice and a half the width of the body), 

 terete, acute, composed of three rows of plates [abactinaUy], which 

 join above by their lateral margins. Beneath each upper lateral 

 row of plates there is an uiferior lateral range [uiframarginal] vis- 

 ible, 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 the 

 removal of the spines covering the surface. 



"The specimen is considerably crushed, and two of the arms 

 broken off at the base; the madreporiform tubercle upon the back 

 is not visible in our specimen. From its condition, the structure 

 can not be entirely made out, but it is sufRciently clear to enable 

 any one to recognize the species." 



Emended description. — Specimen of the usual size (No. 3, Mus. 

 Comp. Zool.) measures: R = 14 mm., r = 3.5 mm., 'K = Ar. The larg- 

 est specimen (Ottawa, Billmgs collection): R = 16 mm., r = b mm., 

 R = 3.1r. The smallest New York specimen (No. 26, Mus. Comp. 

 Zool.): R = 7 mm., r = 2.5 mm., R, = 2.8r. Width of rays at base 

 from 2.5 mm. to 5.5 mm. 



Rays short, tapermg rapidly, convex abactinaUy and flat actinaUy. 

 Disk comparatively large, probably convex abactinaUy during life. 



Abactinal area of rays consisting of 5 ranges of largo, thick, 

 and tumid granular plates. The 3 medial ranges, when not 

 distorted by pressure, conspicuous, with the 11 to 12 plates of 

 each column closely adjoining and considerably elevated above 

 the inframarginal ranges. The proximal plates of each supra- 

 marginal range lie against the large interradial plates and are 

 more or less superposed on the large axiUary margmals. In the 

 center of the disk there is a distinct highly convex plate, around 

 which is arranged a nearly complete ring of seven smaUer pieces 



