Agelacrinidae and Lepadocystinae 443 
from Agelacrinus cindnnatiensis and A. pileus by the absence of 
the great number of small plates that form the periphery in those 
species, and also by having the larger plates of the body, in the 
rim, that surrounds the ends of the rays.” However, the plates 
forming the inner band of the peripheral ring do not appear unusu- 
ally large to me, and the smaller marginal plates seem few in num- 
ber, apparently merely because most of them have fallen off. 
As already mentioned, it is very doubtful whether the tubercu- 
lation can be considered a part of the original ornamentation of 
the thecal plates. The tubercles resemble very much those of 
Dermatostroma papillata, James, although of smaller size and more 
closely approximated. In Dermatostroma papillataj the tubercles 
number about three or three and a half in a length of 1 mm., 
while those on the plates of Agelacrinus faberi number about 
five in the same length. The reason for interpreting these tuber- 
cles as due to the presence of Dermatostroma are the following. 
The tubercles on the plates are arranged more or less in rows. On 
the larger plates, along the posterior margin, these rows appear in 
several cases to pass from plate to plate, and are not interrupted 
at the margin of the individual plates. Where the imbricating 
plates are separated from one another, these tubercles, in a number 
of cases, are seen to be present also between the dislocated plates, 
where evidently they would interfere with the close fitting together 
of the plates during the life of the animal. Moreover, along the 
left anterior margin, the tubercles hide the limits of even the 
larger plates, as though a thin tuberculous stroma had passed 
over these plates, and also over the terminal parts of the anterior 
ray, on to the adjacent parts of the interambulacral area. Finally, 
on some plates, apparently as well preserved at the rest, no tuber- 
cles are present or these are only faintly represented, as though in 
initial stages of growth, while adjacent plates of the same series 
have tubercles. Until other specimens at the same horizon, are 
found, in which the tubercles can be demonstrated as original 
parts of the surface ornamentation, I shall regard this feature of 
the type specimen as due to the presence of some Dermatostroma. 
The only surface ornamentation with which I am familiar 
among Ordovician species usually referred to Agelacrinus or 
Lepidodiscus is that of Agelacrinus pileus, and this appears minute- 
ly and irregularly pitted, rather than tuberculated. 
Under these circumstances, Agelacrinus faberi can not, as yet. 
