1889 - 90 .] Dr Traquair on Fossil Dipnoi and Ganoidei. 399 
according to the traditions of the Glasgow geologists, this species 
is Agassiz’s Gyrolepis Rankinei , the name, having been accompanied 
by no description in the Poissons Fossiles , has no right of priority. 
Drydenius insignis, n. gen. and sp. — When my attention was 
first drawn to the vertebrate fossils of the Borough Lee and Loan- 
head Blackband Ironstone, I attributed certain small jaw-fragments, 
showing peculiar bent cylindro-conical and conspicuous teeth, to 
Gonatodus macrolepis, Traq. ; but after collecting a large number 
of those 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. 
The most entire example I have seen is 4 inches in length, and, 
but for the peculiarity of the dentition to be presently described, 
one would indeed be inclined to refer it to Gonatodus. The scales 
are exactly, as in that genus, nearly smooth, with finely serrated 
posterior margins ; the fin-rays are proportionally rather coarse and 
also smooth ; the cranial roof bones are ornamented with flattened 
tortuous ridges. It is in the bones of the jaws that the peculiarities 
reside, which have induced me to elevate the species also to the 
type of a genus. The hinder part of the maxilla forms a short 
expanded plate, from the middle of the anterior aspect of which the 
narrow anterior or suborbital process extends, so that the tooth- 
bearing margin is posteriorly bent suddenly downwards at a con- 
siderable angle. This margin is set as in Gonatodus with a single 
row of proportionally stout cylindro-conical pointed teeth. The 
dentary element of the mandible is rather stout, and shows on its 
upper margin a row of similar teeth. The splenial element presents 
a dental armature which I have not seen in any other palseoniscid. 
The bone is narrow, rounded posteriorly, concave externally, and 
tapering to a point in front, its upper straight margin being set with 
a single row of short conical pointed teeth. But the inner, or oral 
aspect, shows an area about the middle, and occupying more than 
1 of its length, from which a row of six powerful cylindro-conical 
teeth arises, behind which are three or four small ones. The large 
teeth seem disproportionally large for the small size of the fish, and 
are conspicuous even in the most crushed heads. They are strongly 
curved with the convexity inwards. 
