40 PERMIAN FISHES OF THE GENUS ACENTROPHORUS, 



pavement" effect ; the fin-fulcra in the later species are of par- 

 ticularly massive form ; the pectoral fin is placed higher on the 

 flank than in other fusiform Semionotids, and its attachment 

 gives it a peculiarlj^ " modern " appearance. Fused frontals are 

 also unusual in the family ; and of the characters of the axial 

 skeleton which are shown clearly enough to be worth discussion, 

 the expanded neural spines under the dorsal fin and the great 

 size of the supports of the anal fin-rays seem to be quite peculiar 

 to Acentrophorus. 



In view of all these primitive and individual characters it can 

 no longer be said that Acentrophorus differs from Semionotus only 

 in lacking the median row of acuminate scales in advance of the 

 dorsal fin. It is seen to be very much the most primitive known 

 member of the family Semionotidaa, and is therefore difiicult to 

 incorporate in any scheme on which the genera may be classified. 

 On the whole, however, it would appear to be nearest to the line 

 of ancestry of Lepidotus. )Such a relationship is suggested in 

 many points, in particular in the shape of most of the fins and in 

 other details of their structure, in the excavation of the back 

 along the base of the dorsal fin, and in the tendency toAvards a 

 tritoral form exhibited by the teeth on the vomers. 



My thanks are due to Prof. D. M. S. Watson, who first sug- 

 gested the desirability of re-examining the material of Acentro- 

 phorus in the Hancock Museum at I^ewcastle ; to Mr. J. A. 

 Charlton Deas and Mr. T. R. Goddard for giving me facilities 

 for studying some fine specimens in the Sunderland Museum ; 

 and to Dr. W. E. Oollinge for similar privileges at York. 



Literatiire cited. 



Agassiz, L. 1835. — Poissons Fossiles, vol. ii. 



Fritsch, a. 1894. — Fauna der Gaskohle etc. Bohmens, vol. iii. 



King, W. 1850.— Permian Fossils (Pal. Soc). 



KiRKBY, J. W. 1862.— Ann. & Mag. Nat. Hist. ser. 3, vol. ix. 



p. 267. 

 KiRKBY, J. W. 1864. — Quart. Journ. Geol. Soc. vol. xx. p. 353. 



(Reprinted, 1865, in Nat. Hist. Trans. Northld. & Dhm. 



vol. i.) 

 Newberry, J. S. 1888. — Fossil Fishes, Trias, New Jersey and 



Connecticut (Monographs U.S. Geol. Surv., vol. xiv.). 

 Traquair, R. H. 1877. — Quart. Journ. Geol. Soc. vol. xxxiii. 



p. 562. 

 Woodward, A. Smith. 1895.— Cat. Fossil Fishes Brit. Mus., 



part 3. 



