18 THE ROYAL SOCIETY OF CANADA 



for half its length and thence continuing backward at about one- 

 third its maximum anterior elevation. The anal fin extends from the 

 ventral angulation to the caudal pedicle. Anteriorly it is very deep, 

 pointed below and recurved, narrowing rapidly backward to form a 

 fringe similar in shape to the posterior half of the dorsal fin. The 

 curved anterior margin of the anal fin is three times greater than the 

 front elevation of the dorsal fin. 



The characters of the species may be summarized as follows: — - 

 Fish large, laterally compressed, with a maximum depth equal to 

 three-fifths of its total length; dorsal and ventral margins angulated, 

 the upper angulation nearer to the mouth than to the caudal pedicle, 

 the lower one farther back. Dorsal and anal fins extending from the 

 upper and lower angulations respectively to the caudal pedicle. 

 Anterior end of anal fin acuminate and much extended. Caudal 

 fin deeply cleft, equilobate; its pedicle slender. Pectoral fin small 

 and placed high above the ventral margin. No fulcra on the fins. 

 Scale ornamentation minutely pustulose. Flank-scales rhomboidal, 

 much deeper than broad, with a large, anterior, fusiform inner keel. 

 Scales near the posterior, ventral margin of the trunk, small, oval in 

 outline; those on the upper caudal lobe small, diamond-shaped. 

 Moderately large ridge-scales on the upper lobe of the tail; small 

 ridge-scales in advance of the anal fin. Endoskeletal supports of the 

 dorsal and anal fins short, about equal in number to the fin-rays. 



The specimen occurs in a slab of very fine, dark grey, calcareous 

 sandstone, about two inches thick, and lies, much flattened, in a bed- 

 ding plane, at the mid-thickness of the slab, along which the rock 

 has conveniently split, revealing the fish on the two surfaces thus 

 exposed. All the fin-rays are preserved either on one surface or the 

 other. When present on one surface their impression is left on the 

 other. This is the case also with the small ridge-scales in front of the 

 anal fin, but with the rhomboidal flank-scales, the small oval scales 

 above the base of the anal fin, and the diamond-shaped scales of the 

 upper lobe of the tail the plane of fracture lies between those of the 

 right and left sides of the body exposing them from within. The ridge- 

 scales of the upper caudal lobe have broken along their upper edge, 

 so that their halves are on different sides of the cleavage plane and 

 are also seen from within. 



From the mode of preservation of the specimen, it follows, there- 

 fore, that an inner view only of the flank-scales is presented. Their 

 inner surface, as was to be expected, is smooth. By lifting fragments 

 of these scales the exterior sculpture is seen as well as its impression 

 in the rock. The sculpture consists of minute, closely set pustules 

 which shew a tendency to coalesce and form short, twisted or ver- 



