154 PROCEEDINGS OF THE ACADEMY OP [1884. 



ON THE MUTUAL RELATIONS OF THE HEMIBRANCHIATE FISHES, 

 BY THEODORE GILL. 



§ 1. Introductory. 



In my "Arrangement of the Families of Fishes," (1872, p. 13, 14) 

 before I was aware of the peculiarities of the shoulder girdle, and 

 only knowing the characters assigned to the order by Cope, I 

 retained the Hemibranchii in the order Teleocephali, but in the 

 introductory commentary (p, xxxix) I raised the group to ordinal 

 rank, to which it seems entitled. Prof. Cope, however, is entitled 

 to the credit of having first appreciated the distinctness of the 

 group as a whole, although the characters assigned to it were not, 

 perhaps, of the highest systematic value. As now understood, 

 the order seems to be definable as follows : — 



HEMIBRANCHII. 



= Hemibranchii, Cope, Pfoc. Am. Ass. Adv. Science, v. 20, p. 338, 1872. 

 = Hemibranchii, Gill, Arrangement Families Fishes, p, xxxix, 1873 (Based 



on shoulder girdle). 

 = Hemibranchii, Cope, Proc. Am. Phil, Soc, v. 13, p. 25, 1873. 

 = Hemibranchii, Gill, Johnson's New Universal Cyclopasdia, v. 2, p. 872, 



1877 (defined). 

 = Hemibranchii, Jordan & Gilbert, Syn. Fishes N. Am., p. 387, 1882. 

 Acanthopterygii, fam., auct. plur. 



In the " Arrangement of the Families of Fishes " (1872, pp. 

 13, 14), six families were recognized for the Hemibranchs, whose 

 combinations and correspondence with the families of previous 

 authors are shown in the following abstract : — 



" (H. Gasterosteiformes.) 



( Gasterosteoidea. ) 

 183. OasterosteidcB O aster osteidce, Gthr., i, 1-7, 



134. Aulorhynchidm AulorhynchoidcB, Gill, P. A, N. S. Phil., 1862, 233, 



(Aulostomoidea.) 



135. AulostomidcB Fistulariida, Gthr., iii, 529, 535-538. 



136. MstulariidcB Fistnila/riidm, Gthr., iii, 529-534. 



