AUTHOR S ASSTRACT OF THIS PAPER ISSUED 

 BY THE BIBLIOGRAPHIC SERVICE, DECEMBER 15 



A COMPARATIVE STUDY OF THE BONES FORMING 

 THE OPERCULAR SERIES OF FISHES 



CARL L. HUBBS 



Although the structure and arrangement of the bones com- 

 prising the opercular series of certain species or groups of fishes 

 have been described by many anatomists, no one seems to have 

 consolidated the evidence in a comparative study. After ex- 

 amining their structure in a wide range of fishes, the writer has 

 concluded that they are of a different type in the more primitive 

 malacopterygians, on the one hand, and the specialized acanthop- 

 terygians and their relatives, on the other hand. The Isos- 

 pondyli, the most primitive of the teleosts (as usually defined), 

 have opercular plates and branchiostegal rays similar to those of 

 Amia, which, in this respect as in many others, bridges the gap 

 between ganoids and teleosts. In the other chief groups of soft- 

 rayed fishes — Ostariophysi, Stomiatoidea, Apodes, Heteromi, 

 Lyopomi, Synentognathi, Haplomi, Iniomi — the opercula and 

 branchiostegals are of types apparently derivable from that of 

 the Isospondyli. There is a wide variation in the form and 

 arrangement of these bones in these groups, however, as one 

 might expect from their generalized nature. In the higher 

 groups of teleosts, on the other hand — the Microcyprini, Laby- 

 rinthici, Hemibranchii, Symbranchii, Opisthomi, Salmopercae, 

 and in that vast assemblage of modern types comprising in the 

 Percoidea, or clustering about that group — there is maintained a 

 peculiarly constant arrangement of the branchiostegal rays. From 

 a taxonomic standpoint, the results of this study are most sig- 

 nificant in confirming many of the recent refinements, partic- 

 ularly those suggested by Mr. C. Tate Regan, in the classifi- 

 cation of the Teleostei. 



The primitive structure of the membrane bones which support 

 the outer wall of the branchial cavity, and thus protect the 



