. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 4. — Horns of 4. Viewed from in front and in section. 4«. Viewed from the side. the anterior is convex, so that the section of the horn is plano-convex from base to tip. In side view the horns completely overhang the nasals, and are slightly recurved. The long axis of the horn section is directly transverse. Measurements. 2 • •3 d i 22 »•- 2 Distance between tips of horns, outside measurement. Length of horns meas- ured from tins to median fronto asal suture. Antero-posterior di- ameter of the
. Bulletin of the Museum of Comparative Zoology at Harvard College. Zoology. Figure 4. — Horns of 4. Viewed from in front and in section. 4«. Viewed from the side. the anterior is convex, so that the section of the horn is plano-convex from base to tip. In side view the horns completely overhang the nasals, and are slightly recurved. The long axis of the horn section is directly transverse. Measurements. 2 • •3 d i 22 »•- 2 Distance between tips of horns, outside measurement. Length of horns meas- ured from tins to median fronto asal suture. Antero-posterior di- ameter of the molar- premolar series. Free portion of nasals. Approximate diameter of anterior nares. Length. Breadth. Verti- cal. Trans- Terse. M, coloradensis . f. tichoceras M. dolichoceras M. plaiycera M. Proutii M. .70 .80? .74 M. .16 .13 .09 M. .33 .58 .42 M. .16 .32 .25 .20 M. .31 .34 .37 M. .08 .06 .04 M. .12 .13 .09 M. .075 .11 .075 M. .135 .09 .075 .911 .... The above measurements bring out very clearly tne decrease in the propor- tions of the nasals pari passu with the gradual elongation of the horns. An- other very interesting fact is brought out by the comparison of the transverse and longitudinal diameters of the horns at the base. As we pass from the short to the long horned types, through M. coloradensis, tichoceras, dolichoceras, and platyceras, there is a gradual rotation of the- longer axis of the horn-section from a fore and aft to a transverse plane; the species last named representing the extreme of the transverse type. VOL. XIIT. 11. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Harvard University. Museum of Comparative Zoology. Cambridge, Mass. : The Museum
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