. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. SKELETON. CARPUS. TARSUS. radiale intermedium = scaphoid. = lunare. '^'^^^ I = astragulus. intermedium ) ulnare = cuneiforme. fibulare = calcaneum. centrale = centrale. centrale = naviculare. carpale ^ = trapezium. tarsale ^ = internal cuneiform. carpale ^ = trapezoid. tarsale â â = = middle cuneiform. carpale ^ = magnum. tarsale ^ = external cuneiform carpale â ⢠| carpale ^ \ = unciform. tarsale * tarsale ^ I = cuboid. 177 The pisiform of the carpus is a sesamoid bone (^, a mem- brane bone developed in a tendon as a r
. Text book of vertebrate zoology. Vertebrates; Anatomy, Comparative. SKELETON. CARPUS. TARSUS. radiale intermedium = scaphoid. = lunare. '^'^^^ I = astragulus. intermedium ) ulnare = cuneiforme. fibulare = calcaneum. centrale = centrale. centrale = naviculare. carpale ^ = trapezium. tarsale ^ = internal cuneiform. carpale ^ = trapezoid. tarsale â â = = middle cuneiform. carpale ^ = magnum. tarsale ^ = external cuneiform carpale â ⢠| carpale ^ \ = unciform. tarsale * tarsale ^ I = cuboid. 177 The pisiform of the carpus is a sesamoid bone (^, a mem- brane bone developed in a tendon as a result of strain or pres- sure), while the centrale often fuses with the carpale^ to form the OS magnum. The median or unpaired fins which develop from the dorsal pair of lateral folds and the postanal part of the ventral folds occur only in the ichthyopsida. The result of such a union of folds (p. 172) would be to produce a fin in the median line which, beginning on the back, should continue around the tail and forward upon the ventral surface as far as the vent. Such a continuous fin occurs in the cyclo- stomes, larval amphibia, and many other forms ; but usually it is inter- rupted, and thus divided into dorsal, caudal, and anal (on the ventral sur- face) fins. In the amphibia these fins are without skeletal support; but in the fishes a regular skeleton is formed, consisting of segmentally arranged basalia and radialia like those of the primitive paired fins, and besides, a system of dermal fibrous supports. Occasionally, however, there is to be found an intercalation of radialia, these sometimes being at least twice as numerous as the Fig. 191. Dorsal vertebrse of Pleuracanthus, after Fritsch. c, notochord; h, hasmal arch; n, neural arch; r, radialia of dorsal fin, showing intercalation of ele- Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these
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