240 THE MERYCOIDODONTID/E 



Specific Characters: The skull is about the size of that of the musk deer or about half that 

 of L. ■major. The maximum expansion of the zygomatic arches lies just posterior to the orbit, and 

 they are weaker aft, as is normal, while the malar is moderately deep. The muzzle is short and 

 rather pointed, making the face decidedly narrow in advance of the orbits. The superior skull con- 

 tour is a gentle slope nearly straight from the summit of the inion to the tip of the nasals. The 

 facial vacuities are unmistakably smaller than in L. decora, with their posterior termination but 

 slightly back of the line of the anterior orbital margins. The nasals are relatively wider than in 

 either L. decora or L. major but have the shape usual in this genus. The posterior ends are pointed, 

 forming two wedges in the frontal bones. The lacrimal bone is small facially, with a shallow, but 

 relatively large, depression. The frontals are narrow transversely and short anteroposteriorly. 

 They are elevated slightly along the sagittal plane and more prominently at the supraorbital borders. 

 Apparently they do not extend in advance of the orbits. The closed orbits are elevated as much as 

 in L. decora. The temporal ridges unite just aft of the postorbital constriction to form a long, high 

 sagittal crest. As nearly as can be judged, the supraoccipital crest in this species was similar to that 

 in the others. The brain case is wide and flat, with a decided ridge along the parietosquamosal suture. 

 The external auditory meatus is unusually large and directed backward, as usual, but somewhat more 

 upward than in the other species. The palate is narrow and but slightly vaulted. The open 

 V-shaped palatonarial border is opposite the posterior part of M 3 . The basicranial axis is very shal- 

 low. The glenoid articular surface is much more convex downward than in Merycoidodon. The 

 small postglenoid process is composed equally of the squamosal and tympanic bones, with the divid- 

 ing line in Cat. No. 10122 Y.P.M. a transverse vertical plane. The bulla? are actually as large as in 

 L. major, in fact, they are so greatly inflated that they are separated by an interval that is only 

 2 mm. in diameter. This diameter in L. major is 4.5 mm. The plate-like paroccipital process is 

 dwarfed by the enormous bulla against which it abuts. Index: 0.68. 



Mandible: The symphysiodental angle is about 42°. The angle of the ascending ramus 

 descends but slightly below the lower part of the horizontal ramus. There are no major deviations 

 from generic normalcy, in so far as now known. 



Foramina: The infraorbitals lie above P 4 to the posterior edge of P 3 . The supraorbitals are 

 5 mm. from the mid-line. There are small supplementary foramina in the frontals nearer to the 

 supraorbital borders. Owing to the foreshortening of the basicranial region and to the great develop- 

 ment of the bullas, there have been several changes in the position of the foramina in that region. 

 There is a large foramen just at the internal edge of the inferior articular surface of the occipital 

 condyle. The position suggests that of the condyloid foramen, but it has been much enlarged and 

 moved aft. Anterior to it there is another foramen, lying between the inner edge of the paroccipital 

 process and the bulla. This is the normal position for the foramen lacerum posterius. It is, how- 

 ever, so tiny that I believe that the condyloid carries, in addition to its usual hypoglossal nerve, the 

 glossopharyngeal, pneumogastric, and spinal accessory nerves, or a major portion of them at least, 

 which are normal to the foramen lacerum posterius. The foramen lacerum medium has moved 

 forward transversely, so as to lie almost on a line with the foramen ovale. I cannot detect a 

 foramen rotun-dum. The stylomastoid foramen is elevated and tubular, opening inferiorly on a line 

 well below the postglenoid process. The posterior palatines are opposite to P 4 . 



Dentition: The superior molars differ from those of the other species in that the reduction in 

 size from M 3 to M 1 is much greater, the anteroposterior diameter of M 1 being less than half that of 

 M 3 . The hypocone of M 3 is quite small, while the metastyle is relatively large and prominent. 

 The metacone is rotated inward more strongly than in either L. decora or L. major. The molars 

 are also proportionally wider. The premolars have a more decidedly backward slope from root to 

 crown than in the other species. 



Although Cat. No. 10122 Y.P.M. is a robust specimen, I am inclined to believe that Leidy 

 underestimated the superior molar length. He stated it to be 20 mm., and yet the length of M 1 

 plus M 2 in the type specimen is 1 3 mm. M 3 is absent in the type. In all of the Yale specimens the 

 anteroposterior diameter of M 3 is more than 1 mm. 



