On the Structure and Classification of the Asterolepidi^. 485 



LXIV. — On the Structure and Classification of the Astero- 

 lepidse. By R. H. Teaquair, M.D., F.K.S. 



[Plates XVII. & XVIII.] 



Of this remarkable and problematic group of Palaeozoic Ver- 

 tebrata the genera with which I propose to deal in the present 

 communication are Asterolepis, Eichwald, Pterichthys, Agas- 

 siz, Bothriolejns, Eichw., and Microhrachius^ Traq. We shall 

 commence with 



Pterichthys, Agassiz, 1840. 

 { = Aster olepis, Pander, pars, non Eichw., non H. Miller.) 



The structure of Pterichthys^ sadly misunderstood by 

 Agassiz, was more satisfactorily discussed by Egerton (8) ; 

 but the writer who in former times knew most about it was 

 Hugh Miller. It is, indeed, strange that though Miller pub- 

 lished in 1841 (3) wonderfully accurate figures both of its 

 upper and under surfaces, Agassiz should have mistaken the 

 belly for the back and should have given in his " Old E,ed " 

 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 

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

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

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

 the exact torm 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. 

 Put assuming that Asterokpis, Eichwald, and Pterichthys^ 

 Agassis, are synonymous terms, he added to his elaborate 

 and valuable restoration of the liussian Asterolepis ornatus a 

 tail and dorsal fin taken from tiie 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 *. 



* For instance as ''Pterichthys Alilkri" in Owen's 'Palaeontology' 

 (1860), p. 121, as "■Pterichthys cornutus '' in Prestwich's 'Geolog)' ' (1888), 

 vol. ii. p. 80. 



