82 Grinnell—a new Cretaceous Crinord. 
length, though at what point these first appear is as yet uncer- 
tain. The more distant arm pieces show, when the articular 
surfaces can be examined, a distinct radiate structure, and there — 
are traces, in some of the pieces which are exposed, of a canal, 
which in life may have given passage to the ‘‘axial cord” (nerve) 
of Dr. Carpenter. There is also to be seen on the inner side of 
several of the more distant arm pieces a deep depression, the 
radial furrow, which gives to the plates a subcrescentoid shape. 
These characters cannot be well made out, as all the pieces 
which show them are badly weathered. The arm pieces dimin- 
ish very gradually in size, and the arms are long. On one of 
the slabs they have been traced continuously for a distance of 
eight inches with but little change in size, and it seems probable 
that in life the spread of the outstretched arms may have been 
soon disappearing beneath the arms. A very small uadran- 
gular plate is inserted between the first and second radials and 
the interradial pares which are opposite these. It is not cer 
tain, however, that this arrangement is altogether constant. In 
fact the other side of the specimen from which this is take, 
though too imperfect for use, suggests a larger interradial arm, 
and hence, a probable difference in the number of the plates. 
The interaxillary areas consist of about ten large plates 
and from sixteen to twenty smaller ones, the latter arrange 
much as in the interradial arm. Of the larger ones, seve 
hand. The inferior plate is the largest. It is higher than wide, 
octagonal, and somewhat shield-shaped, apparently support 
on its superior sloping sides two high and rather narrow piece’ 
which in turn, give support to two small subtriangular plates — 
