S8 



THE ANATOMY OF VEETEBRATED ANIMALS. 



nous, and even of the bony, constituents of the pectoral iind 

 pelvic arches of the latter are traceable in Fishes, the cartila- 

 ginous, or ossified, basal and radial supports of the fins them- 

 selves cannot be identified, unless in the most general waj, 

 with the limb-bones, or cartilages, of the other Vertebrata. 



In its least modified form, as in Lepidosiren, the endo- 

 skeleton of the fish's fin is a simple cartilaginous rod, divided 

 into many joints; and articulated, by its proximal end, with 

 the pectoral arch. The Elasmohranchii possess three hasal 

 cartilages which articulate with the pectoral arch, and are 

 called, respectively, from before backward — propterygial, me- 

 eopterygial, and metapterygial basalia. With these are artic- 

 ulated linear series of radial cartilages, upon which osseous, 

 or horny, dermal fin-rays are superimposed. (Fig. 15.) 



Among the Granoid fishes, the fins of Polypterus are, fun- 

 damentally, like those of the Elasmohranchii ; but the pro- 

 pterygial, mesopterygial, and metapterygial hasalia, are more 

 or less ossified, and are succeeded by a series of elongated 

 rudialia, which are also, for the most part, ossified. Beyond 



ma IB.— The right pectoral member of the Mookflsh (,5V!mf/«n): h, pronteryelnm - ma 

 mesopteiyglum ; mi, metapteryglum. "" ' '» •■ "^ 



