90 WHITE AVES ON FOSSIL FISHES FEOM 



(3). The posterior margiu of the tail in Eusthenopteron, as in that of Tristkhopferus, 

 is divided into three distinct lobes, but in the former genus the median lobe of the tail 

 is almost exactly equidistant from the tipper and lower lobes, and not placed mtich 

 nearer the upper lobe, as it is in Tiislichoplenis. 



(4). The larger teeth of Euslhenopteron, or, at any rate their upper halves, appear to 

 be strongly compressed and their lateral margins are thin and sharp, whereas those of 

 Tfisticlwple'us are said to be circular in transverse section. 



"Whether these differences, with some others of minor importance that could be 

 pointed out, are of generic or of only specific importance, remains yet to be ascertained. 



Cheirolepis Canadensis, Whiteaves. 



(Plate VIII.) 



Cheirolepis Canadensis, Whiteaves, 1881. Can. Nat. and Quart. Journ. Sc, N. S., Vol. X, 

 p. 33. 



The following is an amended description of this species. 



Maximum length of the largest specimen collected twenty-one inches, greatest 

 height about one-fifth of the entire length ; general outline elongate-fusiform. Length 

 of the head a little greater than the maximum height of the body ; cranial plates ex- 

 quisitely sculptured with delicate, irregular corrugations, which are crossed obliquely by 

 ribs which are so minrite as to be quite invisible to the naked eye. In some of the cra- 

 nial plates the corrugations consist of wavy ridges of varying length, separated by 

 corresponding but much wider grooves. Occasionally the ridges appear to be made up 

 of a series of confluent tubercles. In other plates the corrugations or ridges anastomose 

 so as to form a dense but irregular network. Margin of orbital cavity circular. Teeth 

 conical, slender, of unequal size. Scales of the body, minute, ganoid, rhomboidal or sub- 

 rhomboidal, about one-third of a line long, and sculptured with acute ribs which radiate 

 longitudinally from the posterior angle of each scale. Scales of the fins and tail nearly 

 rectangular and acutely ribbed at their edges. In the central portions of the fins and 

 tail the scales are twice as long as broad, but near the outer margins of the fins they 

 become much narrower and more elongated. Dorsal fin single, triangular and placed 

 very far backward ; the base of its posterior ray nearly but not quite extending to the 

 commencement of the upper lobe of the tail. Tail heterocercal, its upper lobe fringed 

 by a row of backwardly directed, flattened spines or " fulcral scales," which diminish 

 in length towards the posterior termination of the lobe. Ventral fins situated consider- 

 ably in advance of the midlength and separated from the pectorals by a short interval. 

 Anal fin placed much farther forward than the dorsal, and separated from the ventrals 

 by a space slightly exceeding in length the height of the body at the commencement of 

 the anal. 



The above name was suggested provisionally for a species of Cheirolepis, which 

 resembles the C. macrocephalus ' of McCoy and the C. Cvmmingice of Agassiz in the shape 

 and sculpture of the scales of its body and fins. The ventral fins of C. macrocephalus. 



C. macrocephalus, McCo}', has been shown by Sir P. Egerton to be synonymous with C. Traillii, Agassiz. 



