GLIRES OF THE SANTA CRUZ BEDS. 455 



No. No. 



f5,570 15,882 

 Lower dentition, length -0325 



" Pr- m T .015 



Lower incisor, width .0023 



" " thickness .0025 



Occiput, height 017 



" width at base 026 



Tympanic bulla, antero-posterior diameter 012 



Palate, width at p 003 5 



" "ml 008 



Rostrum, length 019 



" width at base oio 



" " " anterior end 007 



" dorso-ventral height Oil 



Mandible, depth at p T .009 



" " at notch in front of p T .0065 



" thickness at py -0075 



Femur, estimated length from head 058 



" proximal width 013 



" distal width .on 



" width of shaft in middle 006 .0063 



" thickness of shaft in middle 004$ .00$ 



Tibia, proximal width .012 



" " thickness .010 



" distal width .008 



" " thickness .006 



PROLAGOSTOMUS PROFLUENS Ameghino. 



(Plate LXVIII, Figs. 15-18.) 



Prolagostomus profliiens Amegh. ; Enumeracion sistem., etc. ; '1887, p. 1 1. 

 The following description is founded upon a specimen in the collection 

 of the American Museum of Natural History (No. 9,588). In size this 

 species is nearly the same as the preceding one, but is decidedly heavier 

 and more robust. The incisors are distinctly stouter and in the upper 

 grinding teeth the anterior lamina projects more prominently on the 

 outer side. The posterior prolongation of m- varies considerably in size, 

 shape and direction, but it is usually larger than in P. divisus and is di- 

 rected more obliquely inward. The rostrum differs notably in appearance 

 from that of the last named species ; its length is not certainly known, 

 but it is much broader and tapers less anteriorly, yet its dorso-ventral 

 height is less. The unpaired opening between the premaxillae and in 



