APPENDICULAR SKELETON 



215 



In the adult male, the posterior end of the 

 basi-pterygium is produced backwards into a large 

 spout-like process, supporting the clasper. 



Besides the cartilaginous skeleton, homyfibres 

 like those of the median fins are present in great 

 numbers on both surfaces of the fin. 



Eia. 47. — ScyUium canicula. The pelvic girdle and fins of a male 

 specimen, seen from the ventral surface. In the right fln the 

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

 dermal fibres, (a. m. m.) 



D, baai-pterygium. DO, posterior end of the basi-pterygium, forming the 

 skeleton of the clasper. DIF, fin-ray. "F, anterior fin-ray, articulating directly 

 with the pelvic girdle. H, homy fibres. M, muscles. PG, pelvio girdle. 



c. The pectoral girdle, which lies immediately behind 

 the last gill-arch, is considerably larger than the 

 pelvic, and consists of a hoop of cartilage incom- 

 plete above. 



The ventral portion of the hoop is produced 

 forwards into a flattened process, which forms 

 part of the floor of the pericardial cavity, and is hol- 

 lowed dorsally to receive the ventricle of the heart. 



At each side the arch is thickened, and bears 

 on its outer border a triple articular facet for the 

 basal cartilages of the fin. 



