18 



A humerus, scaphoid and astragalus may be referable to this species. They do not 

 differ from those of M. angustigenis, except in their smaller dimensions. 



It is dedicated to Dr. A. R. C. Selwyn, Director of the Geological Survey of the 

 Dominion of Canada, and formerly of the Geological Survey of Victoria, Australia. 



Menodus syceras, Cope. 



American Naturalist, 1S89, p. 628. 



This species is represented by three pairs of coossified nasal bones, one of which sup- 

 ports a horn, in the collection, which I cannot refer to any known species. One of them 

 is smaller and less robust than the other, and as a trace of the median suture still remains, 

 probably indicates a younger animal. 



These nasal bones are flat and not decurved anteroposteriorly, nor vaulted trans- 

 versely. Their free portion is shorter than wide. Accordingly the lateral margins soon 

 begin to thicken downwards. The inferior surface is divided into two grooves by a 

 median, longitudinal, obtuse ridge, which is not found in the M. selivtjnianus. The free 

 border is regularly rounded, with a median notch, and its edge is subacute. The nasal 

 bones are considerably decurved, making an angle with the frontal surface, from which 

 their plane is separated by an obtuse angle which connects the bases of the horns. The 

 bases of the horns are near together, while the horns themselves are erect and moderately 

 divergent. They are of moderate length, and are like those of M. coloradoensis and M. 

 angustigenis, with a longitudinally oval section, flattened at the base on the external side 

 The apex is sub-round in section. 



This species differs from the M. angustigenis in the shorter decurved nasal bones, 

 separated by a transverse angle from the frontal plane. The horns, though similar, are 

 much closer together. It differs in the same characters from the M. coloradoensis. 



Measurements. 



No. 1. 



M. 



Width of nasals at base of horns 116 



Length " from" " 70 



j" Anteroposterior 94 



Diameters of bases of horns 1 



(. Transverse 67 



Width between external bases of horns 160 



Elevation of horn from nasal border 160 



No. 2. 



Length of fragment above 120 



"Width at 30 mm. from extremity 80 



Thickness " " " 25 



No. 3. 



Width at 53 mm. from end 80 



Probable depth of nasal notch 60 



This species belongs to the intermediate group of Menodus, as defined by Messrs. 

 Scott and Osborn, in which both the nasal bones and the horns are of moderate length. 

 They place here M. proutii, Leidy. and M. tichoceras, S. & O. From both of these M. 



