CASTORIDM—STENEOFIBER—S. PANSUS. 453 
The measurements given by Dr. Leidy of Paleocastor nebrascensis show 
it to have been of about the size of Lucastor 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 pansus Cope, Proc. Acad. Nat. Sci. Phila., 1874, 222; Ann. Rep. Wheeler’s Expl. west of 100th 
Merid., 1875, 73. 
Of this species, recently described by Professor Cope, from the Santa 
Fé marls, littleis 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, 0.016; length of first molar, 0".005; width of first molar, 0".004; 
width of last molar, 0".0035; transverse diameter of incisor, 0".004; depth 
of ramus at 2™.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.” 
