Agelacrinidae and Lepadocystinae 
445 
usually is not a specific characteristic but is merely an indica- 
tion of the degree to which these plates are exposed, as the 
result of being drawn apart in a radial direction by means of 
tension. In specimens of Agelacrinus pileus, resting upon an 
inclined surface, for example in figure 1 on plate II, this tension 
usually is along the upper margin of the sloping specimen. In 
specimens resting upon a flat surface, with the outer margin of 
the peripheral ring widely extended, the plates forming the 
inner band of the peripheral ring often are well exposed along 
the entire circumference. In the case of Agelacrinus austini also 
there is, considerable variation in the conspicuousness of the 
plates forming the inner band, and no features are noticed in 
this connection which may be regarded as specific. As in other 
species, the marginal plates are successively smaller, those 
forming the outer row being very narrow and elongated in a ver- 
tical direction. 
Peristomial plates not clearly defined in the specimens at hand 
but believed to include plates corresponding to L, R, and P, in 
figure 5B, on plate I of this paper. 
Inferior aspect of upper part of theca (fig. IB, on pi. 6) as in 
figure 3 on plate II, which is supposed to be the inferior aspect 
of a specimen of Agelacrinus pileus. Floor plates of rays 4 and 
3 distinctly defined along the entire length of the rays. All 
of the floor plates of ray 1 are present; of these the proximal 
floor plate is considerably displaced, and the rest are slightly 
disjointed. They are strongly arched, as viewed from below,, 
evidently consist of a single series of plates along each ray, and 
permit no glimpse of the basal extensions of the lateral covering 
plates. The proximal floor plate of ray No. 3 overlaps the 
adjacent edges of rays No. 4 and 2. 
Specimens found in the upper part of the Whitewater division 
of the Richmond, four and a half miles northwest of Wilmington, 
Ohio, at the Drepanella richardsoni horizon, by Dr. George M. 
Austin, of Wilmington, and belonging to his collection. 
