240 Dr. R. H. Tiaquair on the Structure 



in 1873, he says: — " The position of tliis genus is somewhat 

 douhtfuJ ; tlic t'ulcval armature of all the fins seems to show 

 that its place is here as the oldest nu-niber of the LepidosteiJ 

 series ; but its gular plates^ which Powric has pointed out, 

 indicate possibly a certain relationship with — descent from (?) 

 — the Devonian Polypterini^^*. 



^ly own observations have been made on a large number of 

 examples of the well-known species Ch. Cuvnningicr^ Agass., 

 from Cromarty, Lethen Bar, and Tynet Bum. Besides the 

 specimens in the Edinburgh ^luseum of Science and Art, 

 most of which form part of the Hugh-]\[iller collection, 1 

 have carefully gone over the specimens of Che{roIe2}ifi in the 

 British Museum and in the Museum of Practical Geology, 

 Jemiyn Street ; and I am also specially indebted to the Earl 

 of Enniskillen for having, with great kindness, lent me a 

 number of excellent specimens from his collection. The care- 

 ful examination of these numerous specimens has enabled me, 

 I think, to place the question of the systematic position of 

 Cheirolejn's on a more satisfactory footing than heretofore, 

 though it is to be regretted that, on many points of detail, our 

 knowledge of the cranial structiu-e of this genus is still rather 

 incomplete. 



The key to the whole subject is certainly a knowledge of 

 the structure of Fakrom'scus and its allies ; and had the Avriters 

 who have previously treated of CheiroJepis been better ac- 

 quainted with the structural details of that remarkable grouj) 

 of extinct fishes, the errors and doubts which have so long 

 hung over its affinities would certainly not have prevailed so 

 long as they have. The general form of the body, with its 

 inequilobate, completely heterocercal tail, the number and 

 shape of the fins, with their strongly fulcratcd margins, are 

 common characters, evident to every one without the assistance 

 of the osteology of the head ; only the small size, and appa- 

 rently non-overlapping character, of the scales seemed for long 

 to indicate that its place was with the Acanthodidai. The 

 scales of Cheirolepis, however, are well known to be aiTanged 

 in very distinct oblique rows or bands, following the same 

 general direction from above downwards and backwards as in 

 rhombiferous Ganoids generally, and meeting in acute angles 

 along the dorsal and ventral mesial lines. On the continua- 

 tion of the body-axis along the upper lobe of the caudal fin, 

 however, the direction of these bands is suddenly changed to 



* Dunker und Zittel's ' Palaeontograpbica,' xxii. erste Lieferunp, 

 1873, p. 25, note. 



