C. Wachsmuth—Structure of Paleozoic Crinotds. 185 
group, the plates of the radial series are indented on their upper 
margins more or less deeply for the reception of a protuberance 
from the lower side of the succeeding plate. The indentation 
of the upper margin does not extend throughout the thickness 
of the plate, and in Forbesiocrinus, it is filled by a superficial 
patelloid plate, which is separately articulated and sometimes 
anchylosed with the outer margin of the plate above. This 
peculiarity exists not only in the arm plates, but is conspicu- 
ous in the radials, thus producing apparently an articulate 
structure of the whole skeleton and indicating some degree of 
flexibility in the body as well as the arms. The interradial 
portions appear sometimes depressed, and in other cases swollen 
or bulged out, showing that they probably yielded to a moder- 
ate expansion or contraction of the body walls, due to the mo- 
bility of the radial parts which likewise involves a flexibility 
of the summit. I have not been so fortunate to find the sum- 
. . 
of the interradial series, and which decrease in thickness 
dials, the large first-radials as compared with the succeeding radials, the single 
rs al plate upon which the heavy proboscis rests, indicate that it belongs to Cya- 
on or some allied genus. His 7. gracilis may prove to be Graphiocrinus 
Am. Jour. Rot-—Titkco Santas, Vot. XIV, No. 81.—Sepr., 1877. 
