On the Anatomy and Phylogenese Position of Polypterus. 



415 



branches one of which supplies directly the lower retractor muscle 

 while the other runs through the foramen in the shoulder girdle with 

 the artery to the fin, penetrates the tough connective tissue of the 

 articulation possibly supplying sensory branches to it and then runs 

 on in a ligament along the proximal part of the metapterygium and 

 eventually supplies the deeper protractor muscle. 



Two more spinal nerves reach the fin. The most anterior divides 

 into 2 branches one of which supplies the retractors while the other 

 runs under the metapterygium and supplies the protractors. The last 

 nerve innervates the depressor muscle. 



It is thus seen that 5 spinal nerves supply the fin and of them 

 at least 4 divide into a dorsal branch supplying the dorsal or poste- 

 rior side and a ventral supplying the anterior or true ventral side. 

 This arrangement is strikingly Selachian. 



On comparing the fin of Polypterus with lower animals it is 



Woodcut 8. 



Woodcut 9. 



Woodcut 10. 



m^ 



Woodcut 8. Pectoral fin of Chlamydoselachus from Garman. 



Woodcut 9. Pectoral fin of Polypterus. 



Woodcut 10. Forearm and hand of Ranodon from WiedkrSHEIM. 



1 Scapula. 2 Coracoid. 3 Humeral portion of shoulder girdle. 4 Foramen. 

 5 PropteryK'Um or ulna. 6 Mesopterygium (proximal part) or intermedium and cen- 

 tralia. 7 Metapterygium or radius. 8 Distal part of mesopterygium possibly giving rise 

 to distal carpals. 9 Rays or metacarpals. * Foramen intercarpale. 



Oft* 



