PECTORAL FINS OF POLYPTERUS. 



297 



of the mesopterygium, and the most frequent position 3 ; 3/4 is 

 approximately the apex of the projection. 



I found no superficial indications of a former division of the 

 mesopterygial cai'tilage into a number of blocks, as in Chlamydo- 

 selachus and as described by Pollard *. Blood-vessels pass 

 through the mesopterygial foramina, but I found no nerves going 

 througli them as indicated in Wiedersheim's t illustration. The 



Text-fig. 58. 



Fins of Polypterus. 



A. Fin with forked metapterj'gium. 



B. Fin with epiphysis of propterygium continuous with mesopterygium, 



and small cartilage attached to propterygium. 



number and arrangement of the foramina vary : from one to six 

 were found, of these one or two occur in the mesopterygial 

 ossification, the rest in the cartilaginous part. The ossified 



* Zoologische Jahrblicher, v. 1892, p. 416. 



t Lehrbuch der vergleichenden Anatomie, Erster Theil, 1882, p. 179. 



Proc. Zool. Soc— 1913, No. XX. 20 



