MKRRIAM: TRIASSIC ICHTIIYOSAFRIA. 



59 



shaped with a slender median stein as in the later genera. The coracoid and 

 clavicle may resemble the corresponding bones in certain species of Icltllii/o- 

 minrux, but are generally distinguished by features which are particularly 

 characteristic of Triassic genera. 



77 



78 



Fig. 76. Cymbospontlylus petrinus Leidy. Pectoral arch, X %. Sc, scapula; Co, coracoid; Cl, 



clavicle. 

 Fig. 77. Shastasaiirus osmonti Merriam. Pectoral arch, X %. Sc, scapula; Co, coracoid; Cl, 



clavicle. 



Fig. 78. Delphinosaurus perrini Merriam. Pectoral arch, X %. Sc, scapula; Co, coracoid. 

 Fig. 79. Merriamia zitteli (Merriam). Pectoral arch, X %. Sc, scapula; Co, coracoid. 

 Fig. 80. Mixosaunts cornalianus (Bassani). Pectoral arch, X % Sc, scapula; Co, coracoid; Cl, 



clavicle; Id, interclavicle. (After Repossi.) 



In Mizosaurus and Shastasaurus the coracoid is narrowed or pedunculate 

 proximally, as in Ichthyosaurus communis and in the early Liassic species 

 generally. In Cymbospondylus and Delphinosaurus it is broadly sickle-shaped, 

 the Cymbospondylus type being distinguished by an anterior perforation. In 

 M.erriamia the coracoid is nearly elliptical without constriction or emargina- 

 tion, somewhat as in Ichthyosaurus integer. As far as has been determined, the 

 natural groups into which the Ichthyosauria of the Triassic seem to fall do not 



