L02 GANOID FISHES OF THE CARBONIFEROUS FORMATION. 



The pectoral fin is not seen in any specimen, but the ventrals occupy the normal 

 position as shown in fig. 5. The dorsal and anal fins, somewhat large, are of the usual 

 triangular acuminate contour, the joints of the rays being very slightly longer than 

 broad, and mostly smooth. The caudal is strongly heterocercal, deeply cleft, and 

 inequilobate, and very distinct fulcra are observable on the anterior margins of all 

 the fins. 



Observations. — When my attention was first drawn to the vertebrate fossils of the 

 Borough Lee and Loanhead Blackband Ironstone, I attributed certain small jaw 

 fragments showing peculiar bent cylindro-conical and conspicuous teeth to Gonatodus 

 macrokpis, Traq. ; but after collecting a considerable number of these little dentigerous 

 bones, it began to be clear to me that I had, on the other hand, to deal with a new fish, 

 of which more or less entire specimens with the teeth in situ began also to turn up. 

 These fishes bore, in their scales and fin-rays, a considerable resemblance to Gonatodus, 

 but as I had never seen any trace of such splenial teeth, for such they proved to be, in 

 species of that genus such as G. punctatus, I proposed, in 1890, for this new form the 

 generic term Drydenius, taken from the Vale of Dryden, which lies in close proximity 

 to the ironstone mines of Borough Lee and Loanhead. The salient character of this 

 genus is the peculiar dental armature of the splenial element of the mandible to which 

 the first found "jaw fragments" are clearly referable. 



Geological Position and Locality. — In the Borough Lee Ironstone, a member of the 

 Edge Coal or Middle Carboniferous Limestone Series of the Lothians, worked at 

 Borough Lee and Loanhead, near Edinburgh. 



2. Drydenius Molyneuxi, Traquair. Plate XX, figs. 6 — 8. 



MicitocoNODus Moltnkuxi, Traquair. Ganoid Fishes Brit. Carb. Form. (Pal. 



Soc, 1877), p. 33 (name only). 

 Gonatodus Moltneuxi, Traquair. Geol. Mag. [3], vol. v, 1888, p. 252. 



J. Ward. Traus. N. Staff's. Inst. Mining Engin., vol. x, 



1890, p. 178, pi. vi, fig. 11. 

 A. S. Woodward. Cat. Foss. Fishes Brit. Mus., pt. ii, 

 1891, p. 436. 



Specific Characters. — Attaining a length of little over three inches; scales of flank 

 with very numerous fine denticulations on the posterior border; vascular openings 

 on free surface of scales few or absent; articulations of fin-rays distant. 



Description.— '['he largest specimen of this little fish which I have seen is scarcely 

 more than three inches in length ; the shape is fusiform, rather " stumpy " ; the length 

 of the head is contained about four and a half times in the total. The cranial roof- 



