the Marsh Collection, etc. 449 



parapet. The ratio between the transverse and antero- 

 posterior diameters, measured at the base of the crown, 

 is as follows in the forms listed below: Fells leo { 1 to 1.4, 

 Pseudcelurus, 1 to 1.7, in the true Fells line; while in the 

 macliserodont series, M. necator (based on Cope's figure), 

 1 to 2.2, M. palm Id ens (Blainville), 1 to 2.6, M. niobra- 

 rensis, sp. nov., 1 to 2.4, and Smilodon neogceus Lund 

 (from Burmeister's measurements), 1 to 2.33. M. cras- 

 sldens may be nearer to the felines as indicated by the 

 ratio of 1 to 1.65. Hence it is seen at once that the pro- 

 portions of the canine in the f elid and machaerodont series 

 are very different, and that this new machaerodont is 

 much closer to Machcerodus than to any form in the feline 

 series of equivalent or later geologic age. 



Machcerodus is very brachiocephalic and this new 

 species shows the same character. The anterior part of 

 the alveolus of P 3 is external to a plane, parallel to the 

 sagittal plane, passing through the outermost part of 

 the canine. In the Yale specimen the anterior part of this 

 premolar is offset approximately 6 mm. ; in M . palmidens, 

 about 4 mm. 



This new species differs from the typical Machcerodus, 

 in so far as we have comparable parts from which to 

 judge, in that the incisors are a little more anterior to 

 the canines, thereby making the muzzle slightly more 

 pointed. Another divergence is seen in the incisor pro- 

 portions, the external being larger and the amount of 

 reduction from this one greater than in M. pal nucleus. 



The skull of M. pahnldens is a trifle greater than one 

 half that of Fells leo, while this new species is probably 

 about two thirds the size of the lion and hence smaller 

 than any of the specimens hitherto referred to this genus 

 from North. America. 



Measurements. 



Cat. No. 12829 



M.palmidens Y. P. M. 



mm. mm. 



Width of palate at and including canines . . 47 54 



Width of palate at anterior part of P 3 60 73 



Length of diastema between C and P 3 . . . . 7 11.5 

 Length (axial) from prosthion to line 



through post, of canines 27 38 



