CHAPTER XX. 



THE PECTORAL AND PELVIC GIRDLES AND THE 

 SKELETON OF THE LIMBS. 



TJie Pectoral girdle. 



Pisces. Amongst Fishes the pectoral girdle presents itself 

 in its simplest form in Elasmobranchii, where it consists of a 

 bent band of cartilage on each side of the body, of somewhat 

 variable form, meeting and generally uniting with its fellow 

 ventrally. Its anterior border is in close proximity with the 

 last visceral arch, and a transverse ridge on its outer and 

 posterior border, forming the articular surface for the skeleton 

 of the limb, divides it into a dorsal part, which may be called 

 the scapula, and a ventral part which may be called the 

 coracoid. 



In all the remaining groups of Fishes there is added to the 

 cartilaginous band, which may wholly or partially ossify, an 

 osseous support composed of a series of membrane bones. 



In the types with such membrane bones the cartilaginous 

 parts do not continue to meet ventrally, except in the Dipnoi 

 where there is a ventral piece of cartilage, distinct from that 

 bearing the articulation of the limb. The cartilage is moreover 

 produced into two ventral processes, an anterior and a posterior, 

 below the articulation of the limb ; which may be called, in 

 accordance with Gegenbaur's nomenclature, the praecoracoid 

 and coracoid. Of these the praecoracoid is far the most 



