. The Cambridge natural history. Zoology. SKELETON 475 ventral surface of the clavicle; the latter and the irregularly T-shaped interclavicle being, however, still visible from below. InCryptocIidus the two acromial processes meet each other and form a long ventral symphysis, which meets that of the much-enlarged coracoids, the latter enclosing with the scapulae a pair of roundish foramina. The clavicles are not visible from below; they rest upon the dorsal surface of the scapular symphysis, and the inter- clavicle seems to be suppressed. Young Cryptoclidus (Fig. 113, B) and various species of
. The Cambridge natural history. Zoology. SKELETON 475 ventral surface of the clavicle; the latter and the irregularly T-shaped interclavicle being, however, still visible from below. InCryptocIidus the two acromial processes meet each other and form a long ventral symphysis, which meets that of the much-enlarged coracoids, the latter enclosing with the scapulae a pair of roundish foramina. The clavicles are not visible from below; they rest upon the dorsal surface of the scapular symphysis, and the inter- clavicle seems to be suppressed. Young Cryptoclidus (Fig. 113, B) and various species of Plesiosaurus show intermediate con- ditions. This unique arrangement is correlated with the enormous. Fig. —A, Restored outliues of a Plesiosaurus, x -^V ; B, dorsal view of the pectoral arch of an immature Cryptoclidus, from the middle Oolite ; C, fore-limb of a Plesio- saurus, from the Lias. A, Acromial process of scapula ; 01, clavicle ; Co, cora- coid ; H, humerus ; i, carpale intermedium ; Mi to m^, first to fifth metacarpals ; p, pisiform bone ; R, radius ; r, radial carpal; S, scapula; U, ulna; u, ulnar carpal. development of the fore-limbs, although nothing of the kind has taken place in the Ichthyosauri, which have similar large paddles. The limbs exhibit considerable differences in the various groups of Plesiosauria, but they are all pentadactyle. In the oldest, the Mesosauri and :NTothosauri, the limbs are still of the terrestrial type, although fitted for swimming; the chief bones are still slender and elongated, and none of the five fingers and toes have more than five phalanges, the usual number of which seems to be 2, 3, 4, 5, 3 for the first to fifth digits respectively. In the Plesiosauri the limbs are trans- formed into long hyperphalangeal paddles, unfit for progression on land, rather like those of the Ichthyosauria, with much. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability
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Keywords: ., bookcentury1800, bookdecade1890, booksubjectzoology, bookyear1895
