PECTORAL FINS OF POLYPTBRUS. 



295 



forks broken off from a forked radial (text-fig. 57 A), but none of 

 the other incomplete radials showed signs of having been derived 

 in this way. It seems highly improbable that the forked radials 

 are two radials fused proximally ; the proximal epiphyses and 

 ends are of normal size, the peculiar variation (text-fig. 57 B) 

 whei'e there is probably fusion of two radials shows that forking 

 can occur, for they have divided distally into three. But fusion 

 of radials has almost certainly been found in three fins in the 

 radials next to the propterygium, and these are wide proximally 

 as well as distally. In the table " Fins with Forked Radials 

 only," the one in position 1 5 seems to be of this kind. 



Text-fig. 57. 



Radials of Polypteriis. 



A. Incomplete Eadial, apparent!}' formed from one of the forts of a 



forked Radial. 



B. Radial, probably formed of two fused Radials divided distally 



into three. 



The positions of these foi-ked and incomplete radials on the 

 mesopterygial edge and the relative number of the radials 

 occupying the different positions are of interest. In the tables 

 given below the radials are numbered from the metapterygium, 

 and 1 represents the position of the first radial on the meso- 

 pterygium counting from the metapterygium ; 3/4 indicates 

 that an incomplete radial is found between radials 3 and 4. 



