. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 9. Right humerus, viewed in dorsal and ventral aspects in the plane of the distal end, X 'A- separated from it by the noteh typical of pelycosaurs. Tliis separation, however, is obviously a growth stage only, for in 4-0-16 and a further University of Oklahoma speci- men of uncertain number the notch is closed and an ectepicondylar foramen present. Tlie foramen is otherwise found in pelycosaurs only in Edaphosaurus, and it is stated to be absent in Casca. In Caseci, however, the gap between the tip of the supinato
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Fig. 9. Right humerus, viewed in dorsal and ventral aspects in the plane of the distal end, X 'A- separated from it by the noteh typical of pelycosaurs. Tliis separation, however, is obviously a growth stage only, for in 4-0-16 and a further University of Oklahoma speci- men of uncertain number the notch is closed and an ectepicondylar foramen present. Tlie foramen is otherwise found in pelycosaurs only in Edaphosaurus, and it is stated to be absent in Casca. In Caseci, however, the gap between the tip of the supinator proc- ess and the ectepicondyle is small, and may well have been bridged in cartilage. It is obvious that the ectepicondylar fora- men has developed more than once, in parallel fashion, in early reptiles; its pres- ence here may perhaps be correlated with changes in limb mechanics and muscula- ture, due to increased size, rather than attrib- uted to inheritance from a basal edapho- sauroid ancestor. (Fig. 10). The radius is pre- served (although not too well preserved) in several instances. As noted above, it is short, with a length rather less than three- fifths that of the humerus. Although the effect is in all specimens accentuated by crushing, the bone was obviously relatively thin dorsoventrally, as in pelycosaurs gener- ally. As in the case of other limb bones of Cotylorliynchus, the radius is broad in pro- portion to its length. Tlie proximal articular surface, where preserved, has the appearance of an oval, thin dorsoventrally; presumably it was sub- circular in life. The dorsal (extensor) sur- face of the shaft is convex in section; the ventral surface apparently was flattened. A rugose area for ligament or muscle attach- ment is visible on the lateral edge of the dorsal surface just below the head of the bone. From the head the bone (when un- crushed) constricts to a somewhat thinner shaft. A short distance below the head, however, a ridge arises on the medi
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