Dr. R. H. Traqvair — Devonian Fishes of Canada. 17 



its structure or markings. This head displays the typical Holo- 

 ptychian osteology and dentition, the laniaries of the under jaw being 

 acutely conical, and striated to near the apex : they seem, however, 

 to be round in transverse section. 



Mr. Whiteaves at first referred his Glyptolepis to G. micro- 

 lepidotus of Agassiz, though with some doubt, and even in his 

 subsequent detailed description, in which he adopts the name 

 Quebecensis, he still seems to be uncertain as to its distinctness or 

 the contrary. For he says : " As it seems impossible to decide from 

 the description and figure of G. microlepidotus in Agassiz's mono- 

 graph whether the Canadian species is identical with it or not, it 

 seems safer to give the latter a provisional name until the true 

 specific relations of each shall have been ascertained by a direct 

 comparison of specimens from both sides of the Atlantic." 



There is, however, no need for regarding the name Quebecensis as 

 provisional, so far as any possible identity with microlepidotus is con- 

 cerned. For Mr. Whiteaves's figure shows a true Eoloptychian, and 

 probably a Glyptolepis, whereas Agassiz's G. microlepidotus is not 

 referable to Glyptolepis at all, nor even to the same family. That 

 fish is, as I have shown (Geol. Mag. Dec. III. Vol. V. 1888, p. 514), 

 a true Rhizodont, and is, 1 believe, both generically and specifically 

 identical with McCoy's Gyroptychius angustus. 



Rhizodontid^:. 



Eusthenopteron Foordii, Whiteaves. — The characters which Mr. 

 Whiteaves gives as distinguishing his genus Eusthenopteron from 

 Tristi diopter us, Egerton, are briefly as follows : — 



1. That "the vertebral centra of Eusthenopteron do not se<>m to 

 to have been ossified at all." whereas " in Tristichopterus on the 

 other hand the vertebral centres are stated to be completely ossified." 



2. That the large bones bearing the three ossicles which directly 

 support the second dorsal and the anal fin in Eusthenopteron are inter- 

 spinous in character, whereas "the corresponding bones in Tristi- 

 chopterus are represented as spinous rather than interspinous in 

 their character, and as each abutting directly on the vertebral axis." 



3. The much greater vertical symmetry of the caudal fin in 

 Eusthenopteron. 



4. The presence of two cutting edges in the laniary teeth of 

 Eusthenopteron. 



Reasons 3 and 4 certainly hold good whether they be of generic 

 value or not. But such is not the case with the first and second. 

 For specimens of Eusthenopteron Foordii now before me show 

 undoubtedly the presence of vertebral centra in the anterior part of 

 the body at least, these being in the form of hollow rings as in 

 Rhizodopsis, and I am firmly of opinion that the vertebrae of Tristi- 

 chopterus are in the same condition, and that " in this genus the 

 ossification and segmentation of the vertebral column" was not "com- 

 plete," as supposed by Sir Philip Egerton. And also as regards the 

 large fin-supporting bones alluded to in the second reason, I am 

 equally of opinion that Sir Philip Egerton was in error in consider- 



DECADE III. — VOL. VII. NO. 1. 2 



