482 PROP. ST. GEOKGE MIVART ON THE 



set of parts (pterygia), for the sum total of which the term sjjmpterygium 

 may be employed. 

 (2) Piscine fins are related to the limbs of higher vertebrates as structures which 

 have diverged to a less degree from their primitive condition — and this not 

 only because the piscine body, as a whole, is a more primitive structure, but 

 also because their fins are still used for locomotion in that medium in which 

 their primeval form, the continuous lateral fold, was first developed. 



DESCRIPTION OF THE PLATES. 



PLATE LXXIV. 



Fig. 1. First dorsal fin of Zygcena malleus. 

 Fig. 2. First dorsal fin of Lamna cornubica. 

 Fig. 3. First dorsal fin of Mustelus antarcticus. 

 Fig. 4. Left pectoral fin of ditto. 



a, propterygium ; b, mesopterygium ; c, metapterygium. 

 Fig. 5. Left ventral fin of ditto. 



f, pelvic cartilage. 

 Fig. 6. Caudal fin of ditto. 



p, parapophysial vertebral elements. 



PLATE LXXV. 



Fig. 1. Caudal fin of Lamna cornubica. 



Fig. 2. First dorsal fin oi l^otidanus dnereus. 



b, basal cartilage. 

 Fig. 3. Left pectoral fin of ditto. 



a, propterygium ; b, mesopterygium ; c, metapterygium. 

 Fig. 4. Left ventral fin of ditto. 



b, basal cartilage ; p, pelvic cartilage. 

 Fig. 5. Anal fin of ditto. 



Fig. 6. Fii-st dorsal fin of Scyllium canicula. 

 Fig. 7. Left ventral fin of Ginglymostoma cirratum. 

 b, basal cartilage ; p, pelvic cartilage. 



PLATE LXXVI. 



Fig. 1. Left pectoral fin of Ginglymostoma cirratum. 



cr, coalesced radials; p\ small proximal piece; ^i, propterygium 1 



