216 THE DOG-FISH 



d. The pectoral fin has three basal cartilages, the pro- 

 pterygiiim,meso-pterygiiim,andmeta-pterygium, 



articulating with the three facets on the pectoral 

 girdle. Of these the pro -pterygium is the smallest, 

 and the meta-pterygium, which extends along the 

 inner or attached border of the fin, and corresponds 



Pig. 48.— Scyllium canicula. The pectoral girdle and fins of a male 

 specimen, seen from the ventral surface. In the right fin the car- 

 tilaginous skeleton is shown, in the left the muscles and horny 

 dermal fibres, (a. m. m.) 



A, pro-pterygium. AF, pro-pterygjal fln-ray. B, meso-pterygium. BI", 

 meso-pterygial flu-ray. C, meta-pteryglum. CF, meta-pterygial fln-ray. 

 E, polygonal cartilagiuons plate. H, horny fibres. M, muscles ol fin. 

 PG, ventral portion of pectoral girdle. FCf, dorsal portion of pectoral girdle. 



to the basi-pterygium of the pelvic fin, is much the 

 largest. 



Prom the outer borders of the basal cartilages 

 a series of close- set cartilaginous fin-rays diverge : 

 of these the pro-pterygium supports a single large 

 one J the meso-pterygium also supports one, which 

 is, however, split distally into two or three ; while 



