. Bulletin - United States National Museum. Science. A NEW WHALEBONE WHALE 13. Figure 5.—Ventral view of right periotic, USNM iigj6, o{ Pelocetus calvertensis. Abbrs.: Bo., basioccipital; , exoccipital; , foramen ovale; , jugular notch or incisure; , lateral or descending process of basioccipital; , channel for external audi- tory meatus; , pars cochlearis; Per., periotic; pgl., postglenoid process; , anterior process of periotic; , posterior process of periotic; Pt., pter>'goid; , pterygoid fossa; Sq., squamosal; zyg., zygomatic process. This fene
. Bulletin - United States National Museum. Science. A NEW WHALEBONE WHALE 13. Figure 5.—Ventral view of right periotic, USNM iigj6, o{ Pelocetus calvertensis. Abbrs.: Bo., basioccipital; , exoccipital; , foramen ovale; , jugular notch or incisure; , lateral or descending process of basioccipital; , channel for external audi- tory meatus; , pars cochlearis; Per., periotic; pgl., postglenoid process; , anterior process of periotic; , posterior process of periotic; Pt., pter>'goid; , pterygoid fossa; Sq., squamosal; zyg., zygomatic process. This fenestra ovalis is largely concealed from a tympanic v\ by the overhanging external face of the pars cochlearis. A thin carina intervenes between this channel for the facial nerve and the fenestra ovalis. Small orifices of the semicir- cular canals are visible at the bottom and on the outer wall of the vestibule. There is a deep and narrow groove extend- ing forward from the external rimof the/^nw/ra oi'a/u through the notch between the pars cochlearis and the anterior process. The fossa for the stapedial muscle is rugose, broader than long and extends downward on the internal face of the posterior process and on the external face of the pars cochlearis. A large shallow concavity (pi. 16, fig. 2) for reception of the head of the malleus is situated adjacent and external to the epitympanic orifice of the aquaeductus Fallopii. The precise margins of this articular facet are not clearly indi- cated, but it appears to be continuous externally with the depressed area on the outer denser portion of the periotic. In front of this facet the base of the slender anterior f)edicle of the tympanic bulla is fused with the anterior 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 United States National Museum;
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