. The Ceratopsia. Ceratopsia. THE SKULL. 25 The lachrymals form a part of the lower portion of the anterior border of the orbits. This portion of the orbital border is much thinner and is less projected than that immediately above, which is formed by the prefrontals. In front of the orbit the lachrymal is continued forward between the prefrontal above and the jugal and maxillary below. The antero-inferior angle of the lachrymal is lodged between the nasal and the superior branch of the maxillary, and just at the union of these three elements there is in the type of Triceratops serratus a foram
. The Ceratopsia. Ceratopsia. THE SKULL. 25 The lachrymals form a part of the lower portion of the anterior border of the orbits. This portion of the orbital border is much thinner and is less projected than that immediately above, which is formed by the prefrontals. In front of the orbit the lachrymal is continued forward between the prefrontal above and the jugal and maxillary below. The antero-inferior angle of the lachrymal is lodged between the nasal and the superior branch of the maxillary, and just at the union of these three elements there is in the type of Triceratops serratus a foramen which passes between rather than through any of these bones. The position'of this foramen varies in the different species; in general it is comparable with that of the infraorbital foramen in the mammalia, and its function may have been similar in the two groups. The internal opening of this foramen is partially bounded by the THE NASALS. In the skulls of old individuals the nasals of opposite sides are firmly united by suture. In the types of Triceratops fahellatus and T. serratus, however, they are still separate. Along the median line of the skull the sutural border is very thick throughout the entire length of the nasals. The external surface of the nasals is regularly convex. Each nasal consists of a broadly expanded posterior portion, an elongated superior portion closely ap- plied to, and in old age coossified with, that of the opposite nasal, and a shorter inferior branch, as shown in fig. 19, A and B. The elongated superior branches of the nasals form the roof of the nasal passage anteriorly and support the nasal horn, which, however, has its origin in a distinct and single center of ossification that does not coossify with the nasals until late in life. At their anterior ex- tremities the nasals each send down- ward a short process which overlaps the superior border of the premaxillary. The postero-inferior branch of the nasal is shorter and more slender
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