OSTEOLOGY OF CARNIVOROUS DINOSAURS. 



17 



posterior end it sends out a vertically expanded branch that extends backward and 

 outward and laps along the median anterior surface of the opisthotic (fig. 6). The 

 prootic is bounded superiorly by the parietal, anteriorly by the alisphenoid (orbitos- 

 phenoid of Osborn) and inferiorly by the basisphenoid. 



Lachrymal (la.). — The elements bounding the orbits anteriorly and uniting with 

 the jugals and maxillaries below, and with the nasals and frontals above are here 

 designated as the lachrymals. Osborn in his description of the Tyrannosaurus 

 skull * following Gaupp, called the same bones the adlachrymals, but which corre- 

 spond to the lachrymals of most authors. Since the appearance of that work, 

 Gregory 2 has conclusively shown that paleontological evidence does not support 

 Gaupp's views and reaches the conclusion that "the prefrontal of reptiles is not 

 homologous with the lachrymal of mammals." 



Fig. 8.— Left lachrymal of Antrodemus valens Leidy. Cat. No. 4734, XJ.S.N.M. J nat. size. A, external view; B, 



INTERNAL VIEW, j, END THAT ARTICULATES WITH THE JUGAL; mi, PROCESS THAT UNITES WITH SUPERIOR AND POSTERIORLY 

 DIRECTED PROCESS OF MAXILLARY; Tia, BORDER THAT MEETS THE NASALS. 



The lachrymal in Antrodemus is an unusually robust element, the superior 

 border of which forms a sharp, elongated (antero-posteriorly) elevation on the 

 lateral median borders of the articulated skull. It may have supported, as first 

 suggested by Osborn, 3 "something in the nature of a low dermal horn." 



The roughened surfaces of this portion of the lachrymal (fig. 8) are all indicative 

 of the above conclusion. 



On the external side (fig. 8, A), below the area described above, the bone is 

 excavated, and still further lightened by deep connecting chambers within the 

 heavier part of the bone. The entrance to this chambered region is by two oval 

 openings, the larger one being posterior. 



There is a slender tapering process which extends forward from the hornlike 

 part of the prefrontal which meets the superior process from the maxillary, being 



1 Mem. Amer. Mus. Nat. Hist., vol. 1, new ser., pt. 1, 1912, p. 7. 



2 Joum. Morphol., vol. 24, March, 1913, pp. 3-4; Proc. Paleontol. Soc, vol. 24, June, 1913, pp. 241-242. 



3 Bull. Amer. Mus. Nat. Hist., vol. 19, 1903, p. 701. 



