566 RAMSAY H. TRAQTTAIR ON AMBLYPTERUS, 



Catopterus of Redfield " *. And in Sir Philip Grey-Egerton's brief 

 description of the speciest occurs the following passage: — "The dorsal 

 fin is placed much nearer the tail than in any other species ; in this 

 respect, but in no other, Palceoniscus catopterus resembles the genus 

 Catopterus of Mr. Redfield. The tail is decidedly heterocerque." 

 The eye is also said to be placed forwards, the mouth to appear 

 small, the operculum to be nearly semicircular. 



The smallness of the mouth would in itself be considerable 

 presumptive evidence against the affinity of this species with 

 Palaioniscus, in which the gape is enormously extensive, as it is 

 also, more or less, in the entire family ; it displays, however, another 

 peculiarity which conclusively shows that the position hitherto 

 assigned to it is incorrect. 



However, the specimens usually seen in collections are almost 

 always in so bad a state of preservation, from their very friable 

 nature, that it is not astonishing that such eminent naturalists as 

 Agassiz, Lyell, and Grey-Egerton should have fallen into error as 

 regards its affinities ; indeed they are ordinarily so rubbed and 

 abraded that in many cases it is barely possible to determine that 

 they are the remains of small ganoid fishes. But in the Museum of 

 Practical Geology, Jermyn Street, there is one rather good specimen, 

 and in the collection of the Geological Survey of Ireland there are 

 several others, on examining which I was not a little surprised to 

 find that the tail is not that of Pal&oniscus. The fin-rays are, as in 

 the Palseoniscidae, closely set and articulated throughout, their 

 fulcra being small and numerous ; and the tail is deeply cleft and 

 somewhat inequilobate. But the body-scales stop short in a little 

 rounded " sinus," which projects only a very short distance up into 

 the base of the upper lobe of the caudal fin, and is then followed by 

 rays which are just as elongated as those of the lower lobe. The 

 tail is therefore much less heterocercal than in Ischypterus or 

 Acentrophorus, in fact not more so than in Lepidotus ; so that the 

 retention of this little fish in the family Paleeoniscidae is no longer 

 possible. 



Are we, however, to consider it as the type of a new genus, or 

 can it be received into any previously known ? This question can 

 only be answered to complete satisfaction when fresh specimens are 

 discovered from which the structure of the head can be more fully 

 made out ; and, unfortunately, since the first " find," none have 

 come to light either in the original or in any other locality. Mean- 

 while, if we turn to the figure of Dictyopyge macrura {Catopterus 

 macrurus, W. C. Bedf.), from the Virginian Triassic strata, given in 

 the previously quoted memoir by Sir Charles Lyell, we shall find 

 that there is a very obvious correspondence between it and the 

 Rhone-Hill fish in the form of the tail, and in the structure and 

 position of the fins — so much so that the probability of their 

 belonging to the same genus seems to me very great. Still greater 

 is the resemblance which it bears to the Dictyopyge socialis of 



* Quart. Journ. Geol. Soc iii. (1847), p. 278. 

 t Quart. Journ. Q-eol. Soc. vi. (1850), p. 4. 



