. Bulletin of the Department of Geology. Geology. 322 University of California Publications. [Geology connecting the anterior sides of the bases of the horns the frontals slope backward and downward from the frontal plane anterior to the horns at an angle of about sixty degrees. On those speci- mens showing the portion of the frontal above the orbits the supraorbital foramina (fig. 3) are situated a little behind the middle of the superior side of the orbit, and just in front of the middle of the base of the horn core. They vary from round to long-elliptical in form. Fig. 8.—Ilingoeeros, sp. F
. Bulletin of the Department of Geology. Geology. 322 University of California Publications. [Geology connecting the anterior sides of the bases of the horns the frontals slope backward and downward from the frontal plane anterior to the horns at an angle of about sixty degrees. On those speci- mens showing the portion of the frontal above the orbits the supraorbital foramina (fig. 3) are situated a little behind the middle of the superior side of the orbit, and just in front of the middle of the base of the horn core. They vary from round to long-elliptical in form. Fig. 8.—Ilingoeeros, sp. Frontal region with bases of horn cores. No. 11882. X%. The horn arises immediately above the upper posterior region of the orbit (fig. 4), and the middle of its basal portion is situ- ated almost immediately over the postorbital process of the frontal. It slopes backward and slightly outward with a suffi- cient upward tilt to make an angle of approximately twenty-five degrees with the plane of the frontal above the orbits. In the type specimen a low, rounded ridge which arises from the portion of the horn core base nearest the orbit swings backward over the outer side of the horn, twisting around it at the rate of one com- plete turn in about three and one-half inches. This ridge grows much stronger as it approaches the posterior side of the horn. In the type specimen it is accompanied by a groove which arises just above the postorbital process of the frontal. A second ridge rises behind this grove so that two distinct spiral ridges are present (fig. 1). Excepting the notch formed by the groove between the two principal ridges, the cross-section of the horn core in the type specimen tends to be approximately circular, as it is also in a fragment of a horn (no. 11886) quite certainly referable to this species. Judging from the nearly uniform width at the two ends. Please note that these images are extracted from scanned page images that may have been digitally enhanced for rea
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectgeology, bookyear1902
