GONATODUS. 93 



outwards at an obtuse angle, the apex coming then by another curvature to point 

 upwards (or downwards in the case of the upper jaw). 



The principal feature of this genus is the dentition, which I have only proved so 

 far as the maxilla and the dentary of the mandible are concerned: no trace of the 

 powerful splenial teeth of the allied genus Drydenius is observable in any specimen of 

 any of the three species which I refer to Gonatodus. The general external appearance 

 of these fishes resembles that of fflonichthys, though the dorsal fin is placed a little 

 further back, the joints of the fin-rays are rather more scale-like, and the suspensorium 

 is not so oblique. 



History. — As I have already noted at p. GO (footnote), I found in 1877 that 

 Agassiz's " Amblypterus punctatus " from Wardie Beach was founded on two distinct 

 species, each of which belonged also to a distinct genus. 1 One of these, for which I 

 retained the specific name "punctatus'' formed the type of the present genus Gonatodus, 

 the other, an Etonic/it//ys, was named by me E. intermedins, though I have more 

 recently (p. 67 of the present work) seen reason to include it among the many varieties 

 of E. Robisoni (Hibbert). 



The peculiar dentition of Gonatodus was, however, first described in 1872 by the 

 late Mr. R. Walker, of St. Andrews, in a fish from the Lower Carboniferous oil shales of 

 Pitcorthie, near Anstruther, in Fifeshire, to which he gave the name of Amblypterus 

 anconoachiuodus. That this Fifeshire fish was referable to the same genus at least as 

 Agassiz's "punctatus" from Wardie, was evident from Walker's figures and description, 

 but it was only after his death and the acquisition of his Collection by the Edinburgh 

 Museum, in 1881, that I was able definitely to ascertain that the species was also 

 the same. 



Species. — Excluding " Molyneuxi," which I now refer to Drydenius, there are three 

 British species of Gonatodus, all of which are from the Lower Carboniferous rocks of the 

 Midland Valley of Scotland. As regards foreign species, we may note that two 

 Carboniferous fishes, one American, the other Belgian, have been referred to this genus. 



Gonatodus Brainerdi was the name given, somewhat doubtfully, by the late Prof. 

 Newberry to a fish from the Berea Grits (L. Carboniferous) of Chagrin Falls, Ohio, which 

 was originally named Palceoniscum Brainerdi by Mr. Witt B. Thomas. The dentition 

 does not seem to have been observed, and I can only say that the figure of the entire 

 fish given by Newberry does not in any way suggest the genus Gonatodus. 



More like a species of this genus in general appearance is the fish from the Lower 

 Carboniferous of Viesville in Belgium, named by the late Prof, de Koninck Gonatodus'? 

 Toitliezi — indeed, it was I myself who suggested to that author that it might possibly 

 belong here. But the absence of the head, dentition, and dorsal fin in the specimen 



1 See also the present writer in ' Quart. Journ. Geol. Soc.,' vol. xsxiii, 1877, p. 555, and ' Proc. 

 Eoy. Soc. Edinb.,' vol. ix, 1877, p. 268 et seq. 



