PALAEONTOLOGY OF NEW-YORK. 
&EMJS MARIACRINUS (n.g.). 
Astrocrinites , Conrad in Catalogue, Ann. Geol. Rep. of 1840 and 1841. 
Not Astrocrinites of Cumberland, 1839. 
Not Astrocrinites of Austin, 1843. 
Not Asterocrinus of Munster, 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 
strife 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 Silurian System. Several other species of the 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; 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 
Astrocrinites pachydactylus 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 
Astrocrinites 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 Asterocrinus of Mun¬ 
ster, 1831, that it cannot be used with propriety or without creating some confusion. 
For these reasons, I am induced to adopt another designation, although the mere use 
of the name in a published catalogue could not, under any circumstances, entitle 
the genus to a jfiace in the system. 
