544 Dr. F. A. Bather — On Edrloasteroidea. 



Geological Survey, and be kindly made a search which was at last 

 successful. I have to thank him and the then Director General of the 

 Survey for graciously allowing me to retain this specimen from 1897 

 till the end of 1898. It bears the following labels : — " Agelacrinites 

 Bigsbii / Falls of the Chaudiere / Ottawa Rivr. Canada / Pres. by 

 Dr. Bigsby 1848 / E FA", " M.P.G.," " 6259." The label suggests 

 that Forbes really did fully share the original misapprehension of 

 Billings. 



In 1881 a figure described as "Specimen oi Agelacrinites Diclcsoni 

 from the Cabinet of Dr. Grant" was published as fig. 9 of a plate 

 illustrating "Description of a new species of Porocrinus, &c.," by 

 James Grant, M.D., etc. (Trans. Ottawa Field-Nat. Club, No. 2, 

 pp. 42-4). No reference to the specimen was made in the paper or 

 elsewhere in the number. 



Description of Bigsby's Specimen^. 



The specimen overhangs the edge of a triangular fragment of lime- 

 stone, with sides respectively 56, 70, and 76 mm. long. The rock is 

 composed of fragments of coral, monticuliporoids, and pelmatozoa ; 

 bits of undeterminable brachiopod shells are visible, but I cannot 

 detect the " single spiral univalve " which Sowerby says " is also to be 

 observed." There is, however, on one side a fragment of some sub- 

 cylindrical object, with irregular longitudinal striae on its surface ; 

 it is fully 6 mm. long and 2 mm. in diameter. The whole has the 

 characteristic black tint of Trenton Limestone. The upper surface 

 is curiously weathered, and on it lies a fragment, apparently of 

 a Pleurocystis, with a part of one of the brachioles. The two 

 echinoderms have the actual test preserved in highly crystalline 

 carbonate of lime coloured by iron rust. The rugose surface of the 

 Edrioasteroid may be due to partial solution and redeposition of 

 calcite ; the study, and especially the figuring, of the specimen is 

 thus a task of much difiiculty. The under surface of the specimen is 

 obscured by the matrix, even where it overhangs. An attempt to 

 remove some of this has revealed a few doubtful traces of plates. 

 The posterior and right and left posterior interradii are fairlj' 

 preserved, but the other two are incomplete, and from the left 

 anterior the greater part of the test has been removed. 



The periphery is very obtusely pentagonal ; as to this I do not 

 share Sowerby' s hesitation. The theca rises above the periphery to 

 a height of about 5 mm., which height is attained by the plates of 

 the radial grooves and of the right posterior interradius. The 

 plates in the latter, however, have been raised since death. The 

 above-mentioned traces of plates suggest that the under surface was 

 not flat, and one might hazard a conjecture that the total height of 

 the animal was about 6 mm. ; but it may have been excavated around 

 the abactinal pole. The sagittal diameter was about 20-5 mm. The 

 greatest width, measured along the right posterior interradius and left 

 anterior radius, is 23-5 mm. The length of a side is roughly 11*5 mm. 



On the Upper Surface the five Subvective Grooves radiate with 

 a sinistral curve, which, to a distance of about 6 mm. from the actinal 

 centre, is hardly perceptible, but then becomes more pronounced. 



