Agelacrinidae and Lepadocystinae 
415 
described as quadrangular, but in reality quite irregular in form. 
Rays 1 and 2 (left posterior and left rays) are separated by a long 
narrow plate (Z), equally common to both. If this plate not be 
taken into account, then the first covering plate of the left ray 
(No. 2) is found on the anterior side of the median line, and the 
first covering plate of the left posterior ray (No. 1) is found on the 
posterior or contrasolar side of the median line of this ray. In a 
similar manner, there is a long narrow plate separating rays 4 and 
5 (Y). If this plate not be taken into account, the first covering- 
plate on the right ray is found on the anterior side of the median 
line of this ray, and the first covering plate of the right posterior 
ray is found on the posterior or solar side of the median line of 
this ray. 
There is a tendency toward differentiation in form of the first 
covering plate of the right posterior ray, as defined above. This 
differentiation is connected with the form of the posterior 
peristomial plate, and consists in a slight elevation of the basal 
margin of the covering plate, corresponding to a much more 
marked raising of the lower right-hand margin of the posterior 
peristomial plate (P). Usually the first covering plate of the 
right posterior ray (No. 5) fits snugly against the upper part of 
the right hand margin of the posterior peristomial plate, often 
having a convex outline where adjoining the latter, but posteriori}" 
these two plates do not fit as closely to the anterior outline of the 
immediately adjacent interambulacral plate (X). This suggests 
the possibility of the exit of some duct at the angle between these 
three plates (P, X, and 5). No aperture actually penetrating a 
plate has been noted. 
In Agelacrinus cincinnatiensis , there is either less constancy in 
the form and arrangement of the peristomial plates or the peri- 
stomial areas of the specimens at hand are not infrequently more 
or less distorted, and the plates more or less broken. The original 
of Figure 7, on plate 6, of the Twenty-fourth Annual Report of the 
New York State Museum of Natural History, is by no means as 
distinctly defined a specimen as the drawing suggests. Many of 
the details, including those of the peristomial plates, unques- 
tionably were transferred from other specimens, the identity of 
which is unknown. The plates of the interambulacral areas, with 
the exception of those on the right side of the specimen, are less 
numerous than figured. The peristomial plates, and some of the 
