. Bulletin - United States National Museum. Science. Figure 88.—Views of right periotic (type), USNM 10668, of Parietobalaena palmeri Kellogg: a, ventral view; b, internal view. For abbreviations, see figure 85. that the lengthening of the posterior process continues to physical maturity. Enlargement of the posterior process seemingly cannot be attributed to old age. One physically immature individual (USNM 23203) has the posterior process (length, 90 mm.) unusually expanded toward its distal extremity (greatest diameter, 77 mm.). Epiphyses are ankylosed to the centra of only 3 of the 3
. Bulletin - United States National Museum. Science. Figure 88.—Views of right periotic (type), USNM 10668, of Parietobalaena palmeri Kellogg: a, ventral view; b, internal view. For abbreviations, see figure 85. that the lengthening of the posterior process continues to physical maturity. Enlargement of the posterior process seemingly cannot be attributed to old age. One physically immature individual (USNM 23203) has the posterior process (length, 90 mm.) unusually expanded toward its distal extremity (greatest diameter, 77 mm.). Epiphyses are ankylosed to the centra of only 3 of the 36 vertebrae associated with this specimen. Continued growth of the anterior process appears somewhat limited. The anterior process (pro-otic) is very short, dorsoven- rally compressed distally; the labyrinthic region is enlarged. bulbous, and sculptured (fig. 87a). The relatively short anterior process and the adjoining labyrinthic region are securely lodged in an excavation on the cerebral face of the squamosal. The thin anterior pedicle (fig. 87a) of the tympanic bulla is fused with the epitympanic face of the anterior process in front of the fossa for reception of the head of the malleus. This shallow concavity for the head of the malleus is located either anterior to or alongside (USNM 23055) the epitympanic orifice of the Fallopian aqueduct. Overhang of the obliquely inclined external face of the pars cochlearis conceals the fenestra ovalis from a ventral view. On some periotics (USNM 22995) an anteroposterior crease divides the external and internal portions of the tympanic or ventral face of the pars cochlearis, the outer portion being normally smooth and convex. On other periotics the internal or cerebral portion of this ventral surface is irregularly excavated or depressed (USNM 13874). On most periotics the smooth convex ventral surface of the tympanic face of the pars cochlearis does not extend inward as far as the rim of the internal acoustic meatus. The small fos
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