PAL^EONISCTJS, GYROLEPIS, AND PYGOPTERUS. 555 



form of the anal fin and the structure of the pectoral. In Pygopterus 

 the dorsal is placed nearly opposite the commencement of the anal, 

 commencing only a little in advance of the latter, which is possessed 

 of a remarkably extensive base, being produced posteriorly in a 

 fringe-like manner ; the principal rays of the pectoral are also 

 unarticulated till towards their terminations. It is true that in E. 

 Egertoni and one or two other species still undescribed, these rays 

 are not articulated to the same extent as in E. nemopterus, &c. ; but 

 I feel rather reluctant, on that ground alone, to multiply the number 

 of genera. 



V. Type of A. punctatus, pars (Genus Gonatodus, Traquair). 

 Under the name of " Amblypterus punctatus " three imperfect 

 specimens of fish from the shales of Wardie, near Edinburgh, were 

 figured by Agassiz in the ' Poissons Fossiles.' One of these is a 

 head with the anterior part of the body (Atlas, vol. ii. pi. 4 c. fig. 

 4) ; the second (ibid. fig. 5) wants the head, shoulders, and ex- 

 tremity of the tail ; the third (ibid. fig. 3) displays the entire caudal 

 fin, but is obliquely cut off just in front of the dorsal and anal. 

 But a comparison of these specimens with an extensive series of 

 entire fishes from the same beds establishes the fact that the 

 Amblypterus punctatus of Agassiz was founded upon fragments of 

 two distinct fishes, the specimen showing the head, but without the 

 hinder part of the body, being not only specifically, but even 

 generically, distinct from the other two, in which we have the 

 hinder part of the body without the head. The latter belong 

 to the genus Elonichthys and to a species closely allied to E. 

 striolatus and E. nemopterus, which I propose to call E. intermedins ; 

 but for the former the peculiarity of the dentition requires the 

 institution of a new genus, for which I propose the name 

 Gonatodus *, retaining for the type species the original term 

 "punctatus" For although the enlarged representations of scales 

 given by Agassiz (tab. cit. figs. 6-8) are taken from one of the 

 specimens referable to Elonichthys, yet the name is indeed applicable 

 to both species ; and as the characters of the head and teeth are 

 those which specially distinguish Amblypterus punctatus, according 

 to Agassiz's conception, from his A. nemopterus, with which he con- 

 trasted it as occurring in the same beds, it is, I think, more 

 appropriate to retain his specific name for the fish of which those 

 peculiarities are characteristic. 



The peculiar dentition of Gonatodus was first correctly described 

 by Mr. R. Walker in a fish from the shales of Pitcorthie, Fifeshire, 

 to which he gave the name of Amblypterus anconocechmodus f, a 

 species which is evidently most closely allied to the G. punctatus of 

 Wardie, and possibly identical with it. I have, however, enjoyed 

 no opportunity of comparing with the latter any actual specimens 

 of the Pitcorthie fish. 



The teeth of G. punctatus are from -^ to ^j inch in length in speci- 

 mens measuring from 5 to 6 inches : their form is cylindrical, but 



* yuvv, knee, and odovs, tooth. 



+ Trans. Edinb. Geol. Soe. vol. ii. pt. 1 (1872), pp. 118-124. 



