Glyptocrinus Redefined and Restricted, etc. 219 
The structure and form of the column is frequently of controlling 
generic value, but, in the present classification, there are exceptions 
which subordinate this, possibly, to specific importance only. 
The presence or absence of a proboscis on the vault, or other marked 
difference in its construction, is.of generic importance, but, unfortun- 
ately, the vaults of only a few of these species are known. 
In the light of these preliminary rules, it is proposed that the genus 
Glyptocrinus shall be confined to those species possessing the follow- 
ing three characters, to-wit: basals, five; primary radials, three by 
five; and secondary radials, ane or more by ten. All of the species 
that have been referred to this genus possessing the above three char- 
acters have round columns, composed of thinner and thicker plates, 
except G. fornshelli, and it may be doubtful whether it should be re- 
tained in the genus, for reasons which will be given in the discussion 
of its specific characters. 
Under the generic name of Gaurocrinus, will be included all the 
species possessing the four following characters, to-wit: Basals, five; 
subradials, five; primary radials, three by five; and secondary radials, 
one or more by ten. These species have both round and pentagonal 
columns, but the latter prevail. This genusis primarily distinguished 
from Glyptocrinus by possessing five subradials. G. nealiz will be the 
ty pe. ; 
Under the generic name of Pycnocrinus, will be included those 
species possessing the following characters, to-wit: Basals, five; 
primary radials, three by five, and which do not possess any secondary 
radials. These are primarily distinguished from Glyptocrinus by 
having no secondary radials. The columns are round, the calices 
small, and the vault is supposed to be quite distinct from that of 
Glyptocrinus, though it is too little understood to permit a comparison. 
G. shafferi will be the type. 
Under the generic name of Compsocrinus, will be included those 
possessing the following characters, to-wit: Basals, four; primary 
radials, three by five; secondary radials, two or more by ten; tertiary 
radials, more or less numerous; arms, twenty or more. These are 
primarily distinguished from Glypto .rinus by having only four basals. 
The type is G, harris. 
Having in my collection specimens belonging to nearly all the 
species, and being in possession of many of the types, I propose to 
examine somewhat at length the characters of each species, beginning 
with those which I now refer to Glyptocrinus, and first with the type 
of the genus. 
