CANADIAN FOSSILS. 61 



which are round, and with the large joints ornamented with little 

 pits or coarse striae. It is not certain that these round columns 

 belong to the same species. 



Explanation of Figures. Plate IV. 



Figs. 3a and 36. Two views of the base of a specimen. 



Figs. 3c and 3d. Imperfect plates, to shew the character of the rhombs. 3d has the 

 remains of four rhombs ; 3e is the basal plate of the right side ; 3/ the 

 hexagonal basal plate of the anterior side ; 3g and 3h round columns, 

 with the edges of the large joints pitted. 



Locality and Formation. — Chazy limestone at Caughnawaga, and 

 on the Island of Montreal. 



Collectors. — Sir W. E. Logan, J. Richardson,. E. Billings. 



Genus CoMAEOCTSTiTES, BilUngs. 



(Canadian Journal, vol. ii. p. 269; Geological Survey of Canada, Report, 1856, p. 288.) 



Generic Characters. — Body, ovate, the smaller extremity being the 

 base; pelvis, small, of three plates, above which are from eight to 

 eleven irregular rows of plates, mostly hexagonal ; mouth, near the 

 summit, provided with a valvular apparatus ; arms, free, grooved, 

 and composed of a single series of joints bearing pinnulge ; ambula- 

 cral orifice in the apex between the arms ; column, round and smooth. 

 The plates of the only species that has been collected present, in 

 some conditions of preservation, a peculiar vescicular structure of 

 their exterior surfaces, while sometimes they are solid and smooth. 

 Generic name, comaron, a strawberry. 



X. COMAROCYSTITES PUNCTATUS, BillingS. 



Plate V. 



(Canadian Journal, vol. ii. p. 270 ; Geological Survey of Canada, Report, 1856, p. 288.) 



Description. — The body of this species is of an oval or pyriform 

 shape, and in large specimens about one inch and a-half in length. 

 It is protected by plates which have a deep concavity, occupying 

 nearly the whole of the area of each, the effect of which is to cover 

 the surface of the fossil with large rounded pits, an aspect that serves 

 to distinguish it at the first glance from any other known in the 

 Lower Silurian rocks of Canada. In certain states of preservation 

 the sutures are marked by minute thickly-set square or oblong rough 

 punctuations, which do not however appear to penetrate through to 

 the interior. In some specimens there is only one, and in others 



