CANABIM FOSSILS. 37 



for several lines above the azygos, nearly as wide as the cup, and 

 composed of numerous small plates, which appear to be regularly 

 arranged in upright rows ; the arms bifurcate once immediatly after 

 becoming free, and many times again above ; they are very long and 

 obtusely angular on the back. Below the first bifurcation there are 

 about four joints, and they occupy a length of two lines in a speci- 

 men where the cup is six lines high and the arms two inches and 

 one-fourth long. Their thickness in this part is about half the width 

 of the first primary radial plates from which they spring, and they 

 appear to hold a very deep groove on their inside, as the thickness is 

 greater in that direction than it is in the other ; the column is round, 

 slender and flexible, slightly enlarging near and up to the base of the 

 cup, and composed of alternately thick and thin joints, about six of 

 each in a line of the length ; the plates are without ornament. 



This species so much resembles D. longidactylus (Hall) of the 

 Niagara group that it can scarcely be separated. The principal 

 differences consist in its smaller dimensions, and in the absence of 

 the vertical ridges along the proboscis. On comparing with the 

 illustrations given in the Palaeontology of New York, it will be seen 

 that the second plates of the rays on each side of the proboscis are 

 in fig. la, plate 43, broader than those upon which they rest. In 

 our specimens the second plate of the left-hand ray is equal to the 

 first ; in the right-hand ray it is a great deal less, agreeing in this 

 respect with fig. 7a, plate 42. The species are closely related, and 

 yet I am satisfied they are different. 



Explanation of Figures. Plate III. 



Figure la. Posterior view of a specimen. 

 « 16. The left side. 

 " Ic. Column, enlarged. 



Locality and formation. — City of Ottawa, in the central part of the 

 Trenton limestone. 



Dendeockinus acutidactylus, Billings. 

 Plate III. Figures 2a, 26. 



(Report Geological Survey of Canada, 1856, page 266.) 



Description. — Cup, small, conical somewhat pentagonal ; arms, 

 very slender, several times sub-divided and excessively sharp on the 

 back ; column, round, composed of small nearly globular joints ; 



