FIG. 1. A. Cartoon of pericarotid venous network (PCVN) in a hypothetical marsupial in lateral aspect, with chief components of network in bold type (color scheme also in fig. 3). In addition to transverse basisphenoid sinus, pneumatic sinuses (not separately named) in presphenoid and basioccipital are also frequently present. Six major venous connections involving PCVN components occur in most investigated marsupials at some stage of development and are indicated by italicized letters: a, cs → vps (e.g., Osphranter, fig. 20C); b, cs → icv (e.g., Perameles, fig. 33D); c, icv → bvp (e.g., Monodelphis, fig. 11C); d, rbv → rbv (confluence of antimeres) (e.g., Dromiciops, fig. 16B, C); e, icv → ttcv via cbv (e.g., Caenolestes, fig. 13D); f, ttcv → pvp (e.g., Caluromys, fig. 9E). Smaller accessory connections (e.g., hypophysial and interstitial canaliculi), not separately illustrated, vary considerably among taxa or individuals. Asterisk, craniopharyngeal canal, frequently patent in adult but