11 



II. Magnum. 



M. (?) proulii. M. angusligmis. 



; Vertical 29 31 



Diameters of face . 



[ Transverse 54 50 



{.: 



f Anteroposterior 75 60 



Diameters scaphoid facet .. i 



(. Transverse (.in front) 36 28 



f Anteroposterior 50 45 



Diameters metacarpal facet 1 



{ Transverse (at front) 48 42 



This species appears to be nearest the M. coloradoensis, Leidy, which is only known 

 from a nasal portion of the skull, with the attached horns. The form of the coossified 

 nasals is different in the two specimens, the M. angustigenis having at the extremity an 

 oblique truncation on each side of a median notch, approximately as in Symborodon tri- 

 gonoceras (Menops varians, Marsh), while those of the M. coloradoensis have a gradually 

 acuminate outline. The value of this character is uncertain, but I incline to think it 

 important. What is more important is that the nasals in M. angustigenh have a deep 

 longitudinal concavity below, bounded on each side by a strong marginal rib, both which 

 appear to be wanting in the M. coloradoensis, as Leidy says l the nasals "are thinner" at 

 these borders " than elsewhere." Iu one point they differ from those of any of the species 

 of this genus or of Symborodon which I have seen. The lateral antrum is divided anteriorly 

 into two fossae by a vertical column, which materially strengthens the parts at the 

 anterior base of the horn-core. 



Menodtjs selwyniantjs, Cope. 



American Naturalist, 1889, p. 628. 



This species is founded on the free parts of the coossified nasal bones of a single indi- 

 vidual of smaller size than any of those already described in this report. These parts 

 differ from those of any species known to me. 



The nasals, which are completely coossified, are prominent, narrowed and vaulted. 

 The lateral borders are nearly parallel, and the extremity is rounded. Owing to their 

 great thickness, their profile descends abruptly at the extremity, and the surface is rough- 

 ened as though for the attachment of thickened integument, a small dermal horn, or 

 enlarged muscles. From this tuberosity the surface descends steeply to a thin border. 

 A short distance posterior to the extremity the lateral margins are decurved, forming 

 lateral walls to a deep, longitudinal, median, gutter-like concavity. This is deeper than 

 in any other species. The horns are broken off, and the upper surface of the nasal bones 

 is so little recurved that it is evident that they are not only small, but more posteriorly 

 placed than in the other species. 



- Measurements of Nasal Bones. 



M. 



Length of fragment above 130 



" of nasal border 70 



Width at nareal notch SO 



" near extremity 65 



Depth at apical tuberosity 25 



1 Report U. S. Geol. Surv. Terrs., I., p. 240, plate i., figs 2, 3 ; ii., fig. 2. 

 3 



