. Bulletin of the United States Geological and Geographical Survey of the Territories. Geology. No. 5.] SHUFELDT ON THE OSTEOLOGY OF EREMOPHILA. 121 the same as in the last example (it being, however, the inner facet of two on the tympanies, as a rule), the combined angles, or either of them separately, is very small, or the base and foramen may be found to lie nearly in a plane parallel to the plane upon which the skull rests, or the. angles are 0°. We see then that in the present case, the bearing points being given, the angle of the combined planes is 40°, which fact, even â without actua
. Bulletin of the United States Geological and Geographical Survey of the Territories. Geology. No. 5.] SHUFELDT ON THE OSTEOLOGY OF EREMOPHILA. 121 the same as in the last example (it being, however, the inner facet of two on the tympanies, as a rule), the combined angles, or either of them separately, is very small, or the base and foramen may be found to lie nearly in a plane parallel to the plane upon which the skull rests, or the. angles are 0°. We see then that in the present case, the bearing points being given, the angle of the combined planes is 40°, which fact, even â without actually taking the angles in question, conveys to our minds about the "pitch" or relation of the basi-cranii to the other salient fea- tures of the skull. Taken accurately, these angles, it is obvious, would have a certain vakie when we come to comi^are the various skulls of the class. The primary elements of the occipital, or first cranial vertebra, have become completely fused together, and with such other bony elements of the vertebra beyond, of the mesencephalic arcli, with which they usually articulate. The well-marked superior curved line that limits muscular attachment above would seem to be, and in all probability is, about the position of the lambdoid suture, and the suijerior boundary of the bone we are describing. This curved line descends and is gradually lost along the boundaries of the mastoids and occipitals on either side. Exter- nally and inferiorly we find the occipital pierced by the usual foranuna of the basi-cranii. The group for the exit of the eighth pair of nerves, being the most anterior of all, are situated on either side, in well-marked depressions or pits, some 7 millimetres apart. Back of these and nearer together are the minute precondyloids, looking forwards ami outwards for the i^assage of the hypoglossal nerves. These last foramina are just an- terior to the border of foramen magnum ; this latter aperture is of good size, comparative!
Size: 2209px × 1131px
Photo credit: © Book Worm / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bookcentury1800, bookdecade1870, booksubjectgeology, bookyear1874
