42 



BULLETIN 171, UNITED STATES NATIONAL MUSEUM 



in several of those characters in which it differs from northern forms. 

 Most noticeable among these are the size of the skull and canines, the 

 development of the upper premolars, and the somewhat smaller 

 relative size of the molar. 



Figure 21. — Lutra parricu^pis Gidley and Gazln: Maxillary portion of skull with premolar and molar 

 teeth, type specimen (U.S.N.M. no. 8213), lateral and occlusal views. Natural size. Cumberland 

 Cave Pleistocene, Maryland. 



A comparison of L. jparvicus'pis with L. rhoadsii Cope (1899, pp. 

 238-239) from Port Kennedy, Pa., is difficult on account of the 

 different nature of the materials preserved. L. rhoadsii was based on 

 lower jaws and a single upper molar. The dimensions given by Cope 

 for the anteroposterior diameter of the lingual portion of M^ shows 

 this tooth to be much smaller than in L. parvicuspis. 



Table 10. — Measurements (in millimeters) of superior dentition of three species 



of Lutra 



Measurement 



Length of cheek-tooth series, P' to M', inclusive -.. 



C, anteroposterior diameter of alveolus 



P», anteroposterior diameter. 



P', greatest transverse diameter .- 



P', anteroposterior diameter 



P3, greatest transverse diameter..- 



F*, anteroposterior diameter 



P«, greatest transverse diameter perpendicular to outer wall 



Ml, anteroposterior diameter across outer cusps 



M', anteroposterior diameter across inner portion 



Ml, transverse diameter across paracone and protocone... 



Lutra 

 parrkuspis 

 U.S.N.M. 

 no. 821-3 



(type) 



'34.5 

 •7.7 



5 



4 



7.7 



5.3 

 12.8 

 10.2 



8 



8.7 

 10.5 



Lutra 



canadensis 



U.S.N.M. 



no 197943 



(Div.Mamm.) 



30 



5.5 



5 



3.3 



7.5 



5 

 11.5 



9.6 



8.7 



Lutra 



friina 



U.S.N.M. 



no. 35377 



(Div.Mamm.) 



33. G 

 7.6 

 5 



4.3 

 8.2 

 6 



14.5 



11.5 

 8.3 

 8.5 



11.8 



> Approximate. 



Satherium piscinaria (Leidy, 1873, pp. 230-231) from the late 

 Pliocene or early Pleistocene of Idaho is a considerably larger form as 

 indicated by the size of the tibia. (See also Gazin, 1934, pp. 143-149). 



E. R. Hall (1936, pp. 75-77) regards Lutra parvicuspis as a synonym 

 of L. canadensis lataxina. In examining all the material of this recent 

 subspecies in the National Museum the junior author finds that the 



