114 COMPARATIVE MORPHOLOGY OF VERTEBRATES 



The Shoulder Girdle 



FISHES. — The pectoral or shoulder girdle in the elasmobranchs 

 is more or less U-shaped, the bottom of the arch crossing the ventral 

 surface between the skin and the peritoneal membrane, this ventral 

 portion being known as the coracoid region, which is limited dorsally 







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Fig. I iq. — Diagram of girdles and appendages from the posterior side; upi>er letters, 

 fore limb; lower, hind limb, a, acetabulum; c, carpus; ao, coracoid,/, femur; /», fibula; 

 g, glenoid fossa; h, humerus; il, ilium; is, ischium; mc, mt, metacarpals, metatarsals; p, 

 pubis; pc, procoracoid; ph^~^, phalanges; r, radius; s, scapula; t, tarsus; tb, tibia; u, 

 ulna; 1-5, digits. 



by the point of attachment (glenoid fossa) of the fin. Dorsal to the 

 fossa is the scapular region. Not infrequently the dorsal part of 

 the scapular region is segmented from the rest as a separate supra- 



FiG. 120. — Pectoral girdle and cartilaginous fin skeleton of Scyllium. c, coracoid 

 region; g, glenoid surface; ms, mesopterygium; mt, metapterygium; p, propterygium;r, 

 radialia; s, scapular region. 



scapula. The girdle is usually free from the axial skeleton, but in 

 the skates (raias) the suprascapula articulates with the adjacent 

 vertebrae. 



In the simpler teleostomes (some ganoids, dipnoans) the carti- 



