16 Dr. R. H. Traquair — Devonian Fishes of Canada. 



operculum. In fact, there can be no doubt that the specimen 

 referred to by Mr. Wbiteaves belongs to Eustlienopteron Foordii, 

 and not to Plianeropleur on at all. The " circumorbital " plates are, 

 as we shall see under Eustlienopteron, sclerotic in their nature. 



Ptekichtdyid^;. 

 Bothriolepis Canadensis, Whiteaves. — Kemarks on this species will 

 be found in my paper on the " Structure and Classification of the 

 Asterolepidte," Ann. and Mag. Nat. Hist, for Dec. 1888. 



Cephalaspim:. 



Ceplialaspis laticeps, sp. nov. — Only one specimen, which shows 

 the cranial shield, with badly -preserved traces of the body. Shield 

 proportionately rather broad, length If inch, breadth 2f inches, 

 cornua short : orbits rather close together, oval, large : tesselated 

 divisions of middle layer very small : external surface ornamented 

 by small, smooth, polished and rounded tubercles, moderately close 

 in position. 



This is the first occurrence of a Cephalaspid in rocks of later age 

 than the Lower Devonian, and as such is worthy of the attention of 

 the geologist. 



ACANTHODID^. 



Acanihodes concinnus, Whiteaves. — This is a true Acantliodes, and 

 differs remarkably in the sculpture of the scales from all the other 

 species of the genus. 



MesacantJias affinis, Whiteaves, sp. — At first Mr. Whiteaves was 

 inclined, though doubtfully, to refer this little fish to Acantliodes 

 Mitclielli of Egerton, from the Forfarshire beds ; subsequently, 

 however, he decided to retain it as distinct, though still apparently 

 with doubt, as he speaks only of there being " some reason for 

 supposing that this interesting little fish is distinct from the 

 A. Mitclielli of the Devonian rocks of Scotland." It is, however, 

 only necessary to place specimens of the two forms side by side 

 to see that they are quite distinct, as the scales of the Canadian 

 species are proportionally very much larger than in Mitclielli. 



Owing to the very distinct presence of a pair of small spines 

 intermediate between the pectorals and ventrals in A. Mitclielli, and 

 in A. Peachii, Eg., I have proposed to include them in the new 

 genus Mesacantlius, 1 including also, from its general aspect, A. 

 pusillus, Ag., from the Moray Firth beds, although our specimens of 

 the latter are not well enough preserved to show them. Here I 

 would also place M. affinis, as in one specimen 1 at least imagine 

 I see one of those minute intermediate spines. 



Holoptychiid^;. 

 Glyptolepis Quebecensis, Whiteaves. — The collection in the Edin- 

 burgh Museum contains one head of a small Holoptychian fish which 

 I provisionally refer to this species, although unfortunately no body 

 is present: equally unfortunately, the head in the only specimen 

 described by Mr. Whiteaves is not well enough preserved to show 

 1 Geol. Mag. Dec. III. Vol. V. 1888, p. 511. 



