. Carnegie Institution of Washington publication. 142 FOSSIL IT RTLES OF NORTH AMERICA. Wieland suggested that his type might prove to belong to 0. erosus. However, the latter differs in having thicker bones and a longer nuchal. To illustrate this statement we will consider the seventh peripheral. The length of this is 88 mm., just three-fourths that of the same bone in the type of borealis, yet the thickness of the inner face is 47 mm.—7 mm. more This is too great to be due to age or individual variation. The ths an in the latter species. Width. Per pheral. Length. Height. Thickness. Lower fa
. Carnegie Institution of Washington publication. 142 FOSSIL IT RTLES OF NORTH AMERICA. Wieland suggested that his type might prove to belong to 0. erosus. However, the latter differs in having thicker bones and a longer nuchal. To illustrate this statement we will consider the seventh peripheral. The length of this is 88 mm., just three-fourths that of the same bone in the type of borealis, yet the thickness of the inner face is 47 mm.—7 mm. more This is too great to be due to age or individual variation. The ths an in the latter species. Width. Per pheral. Length. Height. Thickness. Lower face. Upper face [ 10; 60 2J 2 95 60 z 8 ^ 75 45 40 45 4 s QO ;s •• 40 65 1. 104 68 60 5° 7 no 80 72 40 length of the nuchal in borealis is 90 mm. This bone is not present in the type of erosus, but the left peripheral and first costal show that it extended backward at least 90 mm., and it cer- tainly was still longer. If the animal had grown to be a fifth or a fourth larger the nuchal would have been much more than 90 mm. in length. The anterior peripherals of O. erosus are higher than those of the type of borealis, altho the latter belonged to a considerably larger individual. ()n comparing the bones of borealis with those of Cope's supposed sopitus in the American Museum of Natural History no important differences are observed. The nuchals agree. The surface of borealis is marked by pits resembling rain-drop impressions; but the surface of Cope's specimen is so markt to some degree, and a larger specimen referred to the species has such impressions in abundance. Some differences do appear, when careful compari- sons are made among the measurements of the peripherals, but these fall within a few millimeters. Greater differences may be observed between other specimens which are regarded as belonging to 0. borealis. Figures and measurements are presented above of various parts of Wieland's specimen. A portion of these are taken from Dr. Wieland's paper, but most of them ha
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