74 Mr. R. Walker on Fossil Fishes of Dura Den. 



To the description of H. Andersoni perhaps little can now be added 

 (what little may be hereafter added is more likely to affect its 

 generic than its specific character). An additional description 

 of this species has been given by Prof. Huxley in Dr. Anderson's 

 ' Monograph of Dura Den/ and more recently in the ' Tenth 

 Decade of the Geological Survey/ lately published, which con- 

 tains a restoration of Holoptychius, and some descriptive remarks 

 on that genus comprised in Prof. Huxley's excellent ' Preliminary 

 Essay ' on the Classification of the Devonian Fishes. The name 

 H. Flemingii was founded by Agassiz on a piece of a fish which 

 was found in Dura Den, I believe, by Dr. Fleming. It appears 

 to have belonged to a fish of some size — fully larger than most 

 fishes from that quarter. The same species, according to Agassiz, 

 was afterwards found in the " Old Red of Russia/' 



Notwithstanding the distinct figure and clear description of 

 the scales of this species given by Agassiz, it appears to have 

 been overlooked by some geologists, and altogether disregarded 

 as a distinct species by others. On the other hand, some palae- 

 ontologists, while recognizing the distinct character of the scales 

 of H. Flemingii, have asserted that they belonged to some part 

 of H. Andersoni : among the latter was Prof. M'Coy, who was 

 perhaps led into what seems to me to be an error in consequence 

 of the fragmentary condition of his specimens ; in his case, 

 however, it appears the more remarkable, inasmuch as he had 

 correctly observed and described the scales of H. Flemingii in 

 his ' Palseozoic Fossils.' It would seem, however, that he had 

 still doubts about the matter, as appears from the following 

 sentence in the same work, in his description of H. Sedgwickii : 

 " This species, like H. Flemingii, is remarkable for being found 

 on its side, indicating apparently a compressed instead of a de- 

 pressed form ; it also resembles that species in the sculpturing 

 of the scales." Nevertheless it appears to me that H. Flemingii, 

 Agass., is not only a distinct species, but belongs also to another 

 genus, viz. Glyptolepis. In general form H. Flemingii appears 

 to have pretty closely resembled H. Andersoni; but in most 

 specimens, if not in all, it was considerably deeper in proportion 

 to the length. The pectoral and ventral fins appear to be 

 strongly lobated ; the latter, at any rate, in some specimens, were 

 placed fully half their own length in front of the anterior dorsal, 

 which was small, and placed far back. The caudal fin is not 

 very distinctly exhibited in any specimen, but, so far as shown, 

 it appears to be unequally lobed. The scales, as already de- 

 scribed by Agassiz, are, when entire, a good deal higher than 

 long, especially along the sides ; on the dorsal and ventral areas 

 they assume a rounder form. The ornamental lines on the ex- 

 posed parts of the scales, on the sides, extend pretty horizontally 



