CANADIAN FOSSILS. 65 



arm almost precisely the same, but the plates are striated like those 

 of A. temdstriatus. It seems to connect the two species, but until 

 good clear specimens can be examined, it would be the better plan 

 to retain the two names. 



Explanation of Figures. Plate VI. 



Figs. 2a, 26. Right and left side of the Ottawa specimen; m, the mouth. 2c. Left side 

 of specimen from Belleville, shewing a portion of the arm. 2c. The arm en- 

 larged, shewing the ambulacral groove. 2/. View of the top of the arm, 

 shewing the articulating cavities of the pinnulje, and the branches of the 

 ambulacral grooves leading to them. 2d. A plate enlarged, shewing the 

 striae. 



Locality and Formation. — Trenton limestone : one specimen from 

 the city of Ottawa and one from Belleville. The species appears to 

 be excessively rare. 



Collector. — ^E. Billings. 



XIII. Amygdalocystites eadiatus, Billings. 

 Plate VI. Figs. 3a, 3&. 



{Canadian Journal, vol. ii. p. 271, 1854 ; Geol. Survey of Canada, Report, 1856, p. 289.) 



Vescrijption. — Body ovate ; plates somewhat convex, and orna- 

 mented with strong ridges which radiate from the centres to the 

 angles ; mouth ambulacral orifice and arms, unknown ; column 

 round smooth composed of thin joints. 



The spaces between the large radiating ridges are flat and covered 

 with small tubercles, which disappear when the plates are a little 

 worn. 



Of this fine and very distinct species, enough has not yet been 

 found to shew conclusively that it belongs to the present genus. The 

 plates however are solid, or not poriferous, and the shape of the 

 body and column is so much like the other species, in general 

 aspect, that I have referred it to this genus for the present. 



Explanation of Figures. Plate VI. 



Fig. 3a. A specimen crushed flat. 36. One of the plates enlarged. The specimen is 

 worn, and does not shew the granular surface of the spaces between the 

 radiating ridges. 



Locality and Formation. — Trenton limestone, City of Ottawa. 

 Collector. — ^E. Billings. 



