. The Canadian field-naturalist. 194 The Canadian Field-Naturalist Vol. 100 Table 1. Measurements (in mm) of the Type Triceratops prorsus skull from Lull (1933), and the Referred Specimens. Measurements from the orbit in the referred specimens are made from the centre. EMP Greatest length of skull — Greatest width of frill — Distance from orbit to the apex of supraorbital horncore Length of nasal horncore measured along lower side Distance from apex of supraorbital horncore to apex of nasal horncore Greatest diameter of orbit Least diameter of orbit Distance from orbit to apex of rostral
. The Canadian field-naturalist. 194 The Canadian Field-Naturalist Vol. 100 Table 1. Measurements (in mm) of the Type Triceratops prorsus skull from Lull (1933), and the Referred Specimens. Measurements from the orbit in the referred specimens are made from the centre. EMP Greatest length of skull — Greatest width of frill — Distance from orbit to the apex of supraorbital horncore Length of nasal horncore measured along lower side Distance from apex of supraorbital horncore to apex of nasal horncore Greatest diameter of orbit Least diameter of orbit Distance from orbit to apex of rostral Distance from orbit to apex of nasal horncore 763 346 610 224 153 1291 915 YPM No. 1822 SMNH PI 1523 2100 944 1020 550 660' 210 315 650 8501 128 210 122 135 712 955 660 760 'Restored. opening is similar to that in PI though it is not the same shape as in the type. The nasal horncore extends farther dorsally than in either YPM or SMNH specimens. The supraorbital horncores are also erect though not as upright as the nasal horncore. The frill of the specimen is not preserved nor are the jugals, quadratojugals, quadrates or epijugals. An incorrect reconstruction of this area was made by the original preparator. The holotype of T. prorsus and the referred SMNH skull have rugose antorbital ridges which are lacking in the EM specimen. Comments Both the SMNH and EM Triceratops skulls are. Figure 2. Triceratops cf. T. prorsus, EM Right lateral view. Scale bar equals 100 mm. Abbreviations: PmRs — suture between Premaxilla and rostral. similar to the type of T. prorsus and agree with descriptions of this species given by previous authors. The similar shape of the narial openings and orientation and shape of the nasal and supraorbital horncores in these specimens lead me to tentatively identify these skulls Triceratops cf. T. prorsus. Steel (1969: 76) reported that "A fairly generalized central group in which no particular specializations are present seems to
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