1915] The Ottawa Naturalist. 55 



boro, Ontario, (No. 1412), and the beautiful specimen donated 

 by Sir James Grant, and figured by him in 1881. 



The type is a very poorly preserved specimen, as is also the 

 one numbered 1415. This specimen has been cut so as to expose 

 a section across arms II and III, and the section of the anterior 

 arm shows that the strticture is the same as in Agelacrinites 

 pileus, there being a single concave flooring plate, and two roofing 

 plates meeting above the groove thus formed. 



Sir James Grant's specimen of Agelacrinites dicksoni is the 

 finest one of this species which has been found, and it seems 

 undeniable that it belongs to the same species as the specimen 

 described by Dr. Bather. It has the same large pores along the 

 sides of the rays, and the same large inter-ambulacral plates. 

 The super-oral series is well shown, and is of the same type as 

 in Agelacrinites pileus, billingsi, and others. There is a single 

 plate behind the center opposite the anal inter-radius, and two 

 in front, between rays II and III, and III and IV. On each 

 side of the lower plate there are two narrow side plates, and two 

 more small plates outside the upper plates. 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-oral plates seen in the specimen figured by Dr. Bather. 



The inter-ambulacral areas are beautifully preserved in 

 this specimen, showing between the arms the very large plates 

 which are so characteristic of the species, the smaller but still 

 large plates just outside the arms, and the very small plates of 

 the outer border. 



Finally, there is the Bigsby specimen on which Dr. Bather 

 based the genus Lebetodiscus . It agrees with other specimens of 

 A. dicksoni in having five contra-solar rays, subequally spaced, 

 in having the outer covering plates but slightly inter-locking 

 over the rays, in having very large inter-radial plates and in the 

 size and position of the anal structure. It differs in lacking 

 the outer border, but after an inspection of Dr. Bather's photo- 

 graph, one is easily persuaded that that is due entirely to an 

 accident of preservation, as half the known specimens of A. 

 dicksoni lack the border entirely or in greater part. There 

 appears to be a difference between the supra-oral region of the 

 Bigsby specimen and that of the other specimens known. In 

 that specimen the arms seem to be more or less massed together 

 to form a sort of supra-oral disk, somewhat as in L. inconditus. 

 It is not possible to make out the orientation of these plates 

 without seeing the specimen, but as stated above, it seems, 

 possible that the appearance of a large disk is due to the dis- 

 turbed condition of the plates. 



Horizon and locality: — All the specimens of this species 



