258 Wachsmuth and Springer—Silurian Crinovds. 
as we have defined them, or the reference of species thereto, 
in any substantial respect. . 
Mr. Miller expresses the opinion that our “separation of the 
species under this genus Heteocrinus and that of Glyptocrinus, 
o one familiar with the structure such a cross mixture 
their systematic relations, whose importance cannot be under- 
estimated. For this reason, upon questions relating to these 
enera, we attach much weight to the opinions of our Cincin- 
nati friends, who not only are themselves collectors as well as 
investigators, but have access to the other numerous fine col 
lections that have been made in that locality ; and we are grat- 
ified to be able to avail ourselves of the benefit of their 
observations, whether critical or otherwise. In a work of the 
nature of ours, so beset with difficult problems in classification, 
we do not expect to be exempt from error and shall be only 
glad if others are led to the investigation of these questions 
independently, because we are sure that by the operation of 
ifferent minds, considering the subject from other points of 
view, and with other material than ours, a nearer approach 
to correct results will be gained. 
diff 
“naturally fall into two hea: the extremes being represen 
b Veatlt ;” that ‘these two groups are 
