104 PALa:ONTOLOGY OF NEW-tORK. 



OEXDS MARUCRIXIS (n.g.). 



Atroarinites, Covrad in Catalogue, Ann. Geol. Rep. of 1840 and 1841. 

 Not JittrocriniU* of Cumberland, 1839. 

 Not JUrocrinila of AcsTi.v, 1843. 

 Not •/3(<erocrt)iu« of Mi'n'ster, 1831. 



Basal or pelvic plates four. Radial plates three in five series (3X5). 

 Interradial plates three or more. Anal plates numerous. Brachial plates 

 two resting on each third radial ; beyond this point, the structure dif- 

 fers in different species. Surface of plates marked by elevated radiating 

 striae or ridges which are more or less prominent, or by nodes or short 

 spines. 



Arms varying in structure in different species. 



The species constituting the type of this genus is the largest and finest known 

 crinoid in the Siliu-ian System. Several other species of tlie genus are among the 

 most beautiful and interesting forms of all the Silurian and Devonian crinoids. So 

 far as known at present, this genus begins its existence in the Lower Helderberg 

 group, and terminates in the Oriskany sandstone ; giving at least six well cha- 

 racterized species, besides separate plates and columns which indicate the existence 

 of several other forms. 



This genus, in some of its forms, bears a general resemblance to Glyptocrinus, but 

 the number of basal plates is constantly different j and though there are many 

 modifications in the mode of bifurcation of the arms, the species of this genus 

 differ essentially from any species of Glyptocrinus known to me. 



The generic name Astrocrinites was used by Mr. Conrad in his Reports of 1840 

 and 1841, but it is unaccompanied by any description; and though we may suppose 

 it to have been a generic name proposed by himself as new, we are not so informed. 

 Mr. Mather, in his Geological Report of the First District, 1843, uses the name of 

 AstTocrinites pachydacfylus from the Report of Mr. Conrad for 1841. I am not aware 

 that any generic description of this fossil was ever published; and since the name 

 Jlstrocrinites was preoccupied, and has subsequently been used by Austin for a very 

 different form, and at the same time is so similar to the name Asterocrintis of Mun- 

 STER, 1831, that it cannot be used with proijriety or witliout creating some confusion. 

 For these reasons, I am induced to adopt another designation, altliougli tlie mere use 

 of the name in a published catalogue could not, under any circumstances, entitle 

 the genus to a place in the system. 



