ELONICHTHYS STRIOLATUS. 65 



rocks of the Forth Basin, occurring as it does in most of the estuarine fish-bearing beds 

 of that age and region, from the Wardie Shales up to near the top of the Carboniferous 

 Limestone series. But neither in Scotland nor elsewhere have I seen any evidence of its 

 existence in strata newer than the lower boundary line of the ]\[illstone Grit. 



Variations. — The minute account of the form striolatus, which I have already given, 

 may serve as a general description of Elonichthys Robisoni, and I may now enumerate the 

 principal variations in the condition of the fin-rays and sculpture of the scales which are 

 found in what, in the present state of knowledge, must be looked upon as a comprehen- 

 sive and variable species. 



A. Palaotiiscus Robisoni of Hibbert and Agassiz (PL VIII, figs. 2 — 4). — The 

 small Burdiehouse fishes attaining a length of four or five inches to which Hibbert 

 originally applied the term Falaoniscus Rohisoni, and of which Agassiz gave a minute 

 description in the ' Poissons Possiles/ are undoubtedly young individuals of the larger 

 striolatus, which occurs in the same quarry. The sculpture of the scales (PI. VIII, figs. 

 3, 4) is indistinguishable, but the articulations of the fin-rays are more distant, the joints 

 being longer than they are broad, as is the general rule in immature examples of the 

 present family. Professor Young, of Glasgow, first threw doubts on the specific distinc- 

 tion of Robisoni and striolatus, a view with which 1 now perfectly agree. Several points 

 in Agassiz's description require a little comment. Too much stress is laid by him on the 

 " tenuite de son corps," as an examination of any large series of specimens will at once 

 render evident. His statement that " les os de la tete out leurs suifaces lisses; ceux du 

 crane seulement presentent quelques striees peu marquees," can hardly be considered 

 accurate, — the external sculpture of the head-bones being, in Burdiehouse specimens, 

 rarely seen at all ; but where glimpses of it are obtained, it is clear that these bones were 

 ornamented in a manner quite similar to those of its congeners, Agassiz having evidentl}i 

 been misled by the smoothness of their internal aspect. The scales are likewise in all 

 cases more highly ornate than he describes them to be, and the enlarged figures which 

 he gives of them are eminently unsatisfactory. Nor can any value be placed on the 

 supposed greater prominence of the keels on the under surfaces of the scales as a mark 

 distinguishing them specifically from those of striolatus, — such a distinction I have never 

 been able to verify. Young exau)ples of the variety intermedius from other horizons and 

 localities are also indistinguishable from the Burdiehouse specimens. 



The Edinburgh Museum is fortunate in possessing one of Ilibbert's original types of 

 " Palaoniscus Robisoni," namely, the original of fig. 3 on ])1. vii of his memoir on 

 the Burdiehouse Limestone, as well as the specimen figured by Agassiz in the 'Poissons 

 Fossiles,' vol. ii, pi. x a, fig. 1.^ 



The more mature form, Pala:oniscus striolatus of Agassiz, described by myself in the 

 preceding pages as Elonichthp striolatus (Pi. VII, figs. 4 — 15), attains, as we have seen, 



1 These and other type specimens of Carboniferous fitches, iu the collection of the Koyal Society 

 of Edinburgh, were in 1878 generously presented by that body to the Museum of Science and Art. 



