CASTOFJDiE— STENEOFIBER— S. PANSUS. 453 



The measurements given by Dr. Leitly of Palceocastor nebrascensis show 

 it to have been of about the size of Eucastor tortus, or rather smaller, but 

 somewhat different from it in the relative size of the teeth, in the width of 

 the palate, and in the general form of the skull. 



STENEOFIBER PANSUS Cope. 



Steneofiber pansns Cope, Proc. Acad. Nat. Sci. Phila., 1874, 222; Ann. Eop. Wheeler's Expl. west of 100th 

 Mcrid., 1875, 73. 



Of this species, recently described by Professor Cope, from the Santa 

 Ftj marls, little is known. It is apparently closely allied to the <S. nebrascensis 

 of Leidy. Professor Cope's description is as follows: "The molar teeth 

 exhibit a regular gradation in width from the large anterior to the small pos- 

 terior. In the mandibular series, the second and third are broader than long, 

 the first and fourth longer than broad, and with an angle of the outer anterior 

 side of the crown. There is an inflection or groove of the enamel on both 

 inner and outer sides of the crown, and an enamel area before and one behind 

 them, on all excepting the last molar, where there are two in front. First 

 nearly twice as large as last molar. Lower incisor with smooth enamel, and 

 angulate on the extero-anterior border. Ramus stout. Length of the molar 

 series, m .016; length of first molar, ra .005 ; width of first molar, m .004; 

 width of last molar, m .0035 ; transverse diameter of incisor, m .004 ; depth 

 of ramus at 2 m .012. 



"The regular diminution of the size of the teeth from front to rear is 

 characteristic of this species; according to Dr. Leidy, their reduction in size 

 in the S. nebrascensis is more abrupt. The latter species is said to be of 

 Miocene age." 



