6 
MUSEUM BULLETIN No. 31. 
a single concave flooring plate, and two roofing plates meeting above 
the groove thus formed'. 
Sir James Grant’s specimen of Agelacrimtes diclcsoni is the 
largest Agelacrinitid so far found in the Trenton, hut, of course, 
is not so large as some of the Cincinnatian forms. It is 24 mm. in 
diameter, and the centre of the anal pyramid is 5 mm. from the 
centre of the arms. It belongs to the same species as the specimen 
described by Dr. Bather, has the same large pores along the sides 
of the rays, and the same large interambuRacral plates. The supra- 
oral series is well shown, and is of the same type as is A gelacrinibes 
pileus, A. billing si, and others. A single plate lies behind the centre 
opposite the anal inter-radiua, and two lie in front, between rays 
II and III, and III and IY. On each side of the lower plate are 
two narrow lateral plates, and two small plates are outside the upper 
ones. The breaking up of these plates and the introduction of some 
of the proximal ray plates into the disk probably accounts for the 
large number of supra-orals seen in the specimen figured by Dr. 
Bather. 
The inter-ambulacral areas are beautifully preserved in this spe- 
cimen, showing between the arms the very large plates so charac- 
teristic of the species, the smaller but still large plates just outside 
the arms, and the very small ones of the outer border. 
Finally, there is Bigsby’s specimen ion which Dr. Bather based 
the genus Lebetodiscus. It agrees with other specimens of A. dich- 
soni in having five contra-solar rays sub equally spaced, in having the 
outer covering-plates but slightly interlocking over the rays, in hav- 
ing very large inter-radial plates, and in the size and position of the 
anal structure. It differs in lacking the outer border, but on inspection 
of Dr. Bather’s photograph, one is easily persuaded that that is due 
entirely to an accident of preservation, as half the known specimens 
of A. dichsoni lack the border entirely or in greater part. There 
appears to he a difference between the supra-oral region of Bigsby’s 
specimen and that of the other individuals. The arms seem to be 
more or less massed together to form a siort of supra-oral disk, some- 
what as in Isorophus inconditus. The orientation of these plates 
cannot be determined without the specimen, but as stated above, it 
seems probable that the appearance of a large disk is due to the dis- 
turbed condition. 
Horizon and Locality. All the individuals of this species whose 
exact locality is known have been found in the Cystid beds of the 
Prasopora zone, and about 180 feet below the top of the Trenton. 
Besides Peterborough and Ottawa, Pakenham, Out., has furnished a 
specimen listed by Dr. Ami. The specimens from Kirkfield identified 
by Mr. Springer as this species are almost if not entirely all Camey- 
ella mulUbrachiata. 
