182 THE ANATOMY OF VERTEBRATED ANIMALS. 



A 



_ ITa. 



JPmx. I 



2^c. 



FTi. 





•30 



FTj. 



Fia. 68. — ^Diagram showing' the structure of the most important parts of the skeleton of 

 Plesiosuurus. — A, the skull: JSTa, nasal aperture. — B, the left fore-limb: IT, humerus; 

 U, ulna ; E, radius ; r. i. u., radiale, interm.edium, and ulnare, in the proximal row of 

 carpal bones; 1, 2, 3. distal carpal bones; Mc, metacarpus; Ph. phalanges. — C, a dorsal 

 vertebra with ribs {R.\ and ventral ossifications ( V.o). — D, the left hind-limb : F, femur; 

 T. tibia; F, fibula; t. i.f., tibiale, intermedium, and fibulare, in the proximal row of tar- 

 sal bones ; 1, 2, 3, distal tarsal bones ; 3It metatarsus ; PA, phalanges. — E, the pectoral 

 arch : Sc, scapula ; Co, coracoid ; a, clavicles and interclavicle (?). — P, the pelvic arch : 

 /*6, pubis ; II, ilium ; Is, ischium. 



but there is a well-developed system of ossifications of the 

 wall of the abdomen, arranged in transverse rows from before 

 backward ; each row consists of a median bone, slightly bent 

 upon itself, thick in the middle, and thin at each end — and of 

 six other bones, three on each side, which are elongated and 



