. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ROMER: BKAINCASE 99. pop Fig. 4. Ventral view of the braincase; the pituitary region is imperfectly preserved. Abbreviations as in Figure 1. X V2- Posteriorly the braincase extends to a j^reater depth tliaii in typical modern elasniobranchs, for the paired anterior con- tinuations of the dorsal aorta ("common carotids") entered the braincase floor a short distance anterior to the condyle. Well forward in the otic region a pair of openings presumably mark the exit of the carotids from the aortic c
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. ROMER: BKAINCASE 99. pop Fig. 4. Ventral view of the braincase; the pituitary region is imperfectly preserved. Abbreviations as in Figure 1. X V2- Posteriorly the braincase extends to a j^reater depth tliaii in typical modern elasniobranchs, for the paired anterior con- tinuations of the dorsal aorta ("common carotids") entered the braincase floor a short distance anterior to the condyle. Well forward in the otic region a pair of openings presumably mark the exit of the carotids from the aortic canals, and, as may be seen from the plate, there is evidence of gi-ooves — presum- ably for internal carotids — leading from these foramina for- ward and medially toward the hypophysial region. Farther forward on each side is a foramen which may have been the point of entrance of the hyomandibular (pseudobranchial) artery. Still farther forward on either side is a further open- ing, from wliich a deep groove leads forward and outwai-d into the oi'bit; presumably this was for an external carotid. It is unfortunate that almost the entire surface layer of calcified cartilage has been lost in the hypophysial region; how- ever, it is reasonable to believe that the surface of the matrix essentially follows the surface contours. There was here a large oval depression, which may have contained an open hypophysial pit. Paired leading forward from the front end of this depression suggest that the two internal carotids entered the braincase independently Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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