'24 Proceedings of the Boyal Physical Society. 



Eed " such an utterly bizarre and incorrect restoration, which 

 has, moreover, been copied and recopied into so many text- 

 books, down even to the present day. 



A brief account of Pterichthys was given by M'Coy in his 

 "Palaeozoic Fossils," in which Hugh Miller's ideas as to the 

 number and arrangement of the plates of the carapace are 

 tjorroborated. No attempt is, however, made to go into the 

 structure of the pectoral appendages, while as to the head he 

 says that it is " covered by several irregular polygonal pieces, 

 the exact form of which is still doubtful." The fin observ- 

 able on the tail was regarded by M'Coy as an anal (6, p. 598 

 et seq.). 



Pander, in his classical " Placodermen " (7), has given some 

 figures of Scottish examples of Pterichthys, which, however, 

 do not help us much with those details not already known. 

 But assuming that Asterolepis, Eichwald, and Pterichthys, 

 Agassiz, are synonymous terms, he added to his elaborate 

 and valuable restoration of the Eussian Asterolepis ornatus a 

 tail and dorsal fin taken from the Scottish Pterichthys (pi. v., 

 fig. 10) ; and I must agree with Lahusen (11) in protesting 

 against this figure having been reproduced in various works 

 not only as " Pterichthys " but even as one or other of the 

 species of Pterichthys occurring in Scotland.^ 



There is therefore abundant reason for going afresh into 

 the anatomy of the organisms discovered by Hugh Miller, 

 Malcolmson, and Stables, and named by Agassiz Pterich- 

 thys. The special structure of the head and limbs was 

 hitherto almost unknown, and there is also room for rectifica- 

 tion as regards the body-carapace and tail. And this 

 investigation is also of great systematic importance as bear- 

 ing on the question as to whether Pander was right in 

 maintaining the identity of Agassiz's genus with Eichwald's 

 Asterolepis ; for as " Asterolepis " has the priority, the only 

 ground for maintaining Pterichthys, were Pander right in 

 his contention, would be the inadequacy of Eichwald's 

 original description of Asterolepis, and then that name would 



1 For instance as '^Pterichthys Millcri" in Owen's "Palaeontology" 

 (1860), p. 121, as ''Pterichthys cornuttcs" in Prestwich's "Geology" (1888), 

 vol. ii., p. 80. 



