Glyptocrinus Redefined and Restricted, etc. 217 
| GEYPTOChINUS REDEFINED AND RESTRICTED, 
GAUROCRINUS, PYCNOCRINUS AND COMPSOCRIN- 
OS HSTABLISHHD, AND TWO NEW SPECIES DE- 
SCRIBED. | 
By 8. A. Minter. 
The species that have been referred to the genus Glyptocrinus in- 
clude a great diversity of forms possessing essential differences in con- 
struction, if we place reliance upon the order oft arrangement of the 
plates, in either the columns, calices or arms. The grouping is such 
that no single generic character can, with certainty, be ascribed to all 
the species. Of course, sooner or later, they will be arranged in dif- 
ferent genera; to do this, however, successfully, at this time, is not an 
easy task. | 
A partial subdivision may be accomplished, and to this end the 
present article is devoted. Those from the Upper Silurian will not be 
discussed, because we are not sure that any of them belong to Glypto- 
crinus, and because we have not at hand suitable specimens for ex- 
amination and description. The remarks will be confined, therefore, 
alone to those occurring in the Lower Silurian rocks of this country. 
Messrs. Wachsmuth and Springer have made G. lacunosus the type 
of the genus Archeocrinus, and included in it, G. marginatus. This 
genus is distinguished from Glyptocrinus by its .ssubglobular form, 
large basals, and wide interradial areas. The arms become free at the 
second or third secondary radials, are short, widely separated, and _ bi- 
furcate soon after becoming free. The column is composed of very 
thick projecting plates, separated by very thin ones in the upper part, 
but lower down becomes smooth. The vault is unknown, but it is 
doubtless different from that in Glyptocrinus. The genus may be 
readily recognized, and was properly made. 
G. quinquepartitus was founded upon a subpentagonal, quinquepar- 
tite column, composed of alternately thicker and thinner plates, and 
as nothing more is known of it, it will not be further considered. 
G. dyeri var. sublevis is distinguished from G. dyeri only by the 
absence of the sculpturing on the plates of the calyx, and as this may 
not have existed during life, or may have resulted from age, accident, 
injury, or later chemical or mechanical action, it may not be of even 
varietal signification, hence it will not require further notice. 
The species described by Prof. Wetherby, under the name of Refeo- 
