PECTORAL FINS 



243 



(Fig. 146, G) is uniserial, closely resembling that of the more 

 typical Elasmobranchs. 1 There are three basal elements, a pro- 

 pterygium, a mesopterygium, and a metapterygium, each of 

 which supports a series of partially ossified radialia. Little is 



FIG. 146. Pectoral fins of various Fishes. A, Acanthias ndgaris ; B, Raia sp. ; 

 C, Chimaera monstrosa ; D, Acipenser rhyncJuteus ; E, Amia calva ; F, Lepidosteus 

 platyrhynchus ; G, Polypterus bichir ; H, Salmo salvdinus. The preaxial side of 

 each fin is to the left and the postaxial to the right, f.r, Dermal fin-ray ; 7/w, 

 mesopterygium ; ml, metapterygium ; jj, propterygium ; r, free radialia ; 1, 5, the 

 preaxial and postaxial basal elements in a Teleost, which may be mesopterygial and 

 metapterygial pieces respectively, the three remaining basal pieces probably being 

 intrusive metapterygial radialia directly articulating with the pectoral girdle. In 

 B, D, E, and F, similar intrusive radialia are shown. (From Gegeubaur.) 



known of the endoskeletal elements of the broadly or acutely 

 lobate fins of the fossil Crossopterygii, but it seems probable 

 that their disposition was uniserial and abbreviate in obtusely 

 lobate fins and biserial in acutely lobate fins. In the remaining 

 Teleostomi (Actinopterygii) the endoskeletal elements become 



1 Budgett, Trans. Zool. Soc. xvi. Part vii. 1902, p. 328. 



