CANADIAN FOSSILS. 79 



little sloping outwards. Their length is about twice their breadth, 

 and they are so disposed that the greater dimension is transverse or at 

 right angles to the groove; the extremities which lie next to the 

 grooves are angular, and some of them appear to have the contiguous 

 pores partly excavated in them. The oral plates are acutely trian- 

 gular, the sharpest angle being towards the mouth. The plates are 

 smooth. The ambulacral pores are very large, and the ossicles are 

 much contracted in the middle and greatly expanded along the 

 median line of the bottom of the groove. 



The most perfect specimen is one inch in diameter measured 

 between the tips of the rays ; diameter of disc three lines ; width of 

 ray at mid-length two lines and a half. 



Dedicated to J. W. Salter, Esq., Palaeontologist of the Geological 

 Survey of the United Kingdom. 



Explanation of Figures. Plate X. 



Figure la. — Ventral view of a specimen collected at Belleville. 

 lb. — The same enlarged. 



Locality and Formation. — Belleville, Canada West. Trenton lime- 

 stone. 



Collector. — E. Billings. 



IV. Stenaster pulchellus, Billings. 

 Plate X. Fig. 2. 



(PalcBaster pulchella, Geological Survey of Canada, 1856, p. 292.) 



Description. — Rays long, slender and sub-cylindrical ; adambula- 

 cral plates transversely oblong ; grooves narrow ; dorsal plates small 

 and tubular. Diameter of the only specimen in the collection two 

 inches and one-fourth measured between the tips of the rays ; rays 

 one inch in length, and two lines and a-half in width at the base ; 

 disc three lines and a-half in diameter. 



Explanation op Piguee. Plate X. 

 Fgure 2. — Ventral view of the only specimen collected. 



Locality and Formation. — Ottawa. Trenton limestone. 

 Collector. — E. Billings. 



Genus Peteaster, Billings. 



Generic Characters. — This genus has both marginal and adambula- 

 cral plates, with a few disc-plates on the ventral side. The general 



