CASTORIDAI—STENEOFIBER—S. NEBRASCENSIS. 451 
ingly well-marked differences will be found in other features of the skull 
when we are able to study this interesting form from more nearly perfect 
specimens. 
The following table, showing the comparative measurements of Ewcastor 
tortus with the corresponding portion of the skull of Castor fiber, is from Dr. 
Leidy’s memoir on the “ Extinct Mammalia of Dakota and Nebraska” (Journ. 
Acad. Nat. Sci. Phila., 2d ser., vol. v, p. 342). 
C. tortus. C. fiber. 
Lines. Lines. 
HEP iMmonmspaceoecupied Dy fOUL MOlars'. 2. ssssse0c< csc. csccce eoccsewescoc caccemece=ce 6+ 13 
Menpihobniatue Mromdfirst Molar tOINCISOLS.. -.2--. <s-s-. wsscnc conc ccscneccesss essere 12 21 
EYcAE Ons aAceOppOsibe Tirsh) MOlATSS 2. so. cso scersocacsasscse ee aee.ccncbiscacesscscelsces 7 14 
Breadth of face in advance of infra-orbital foramen ...... .....2-- sos2---e cnn s encenecnns 53 11 
Wwidubien paluce, betweentirst Mmolars'..o225.-.20- csc ssc. soos ctes eo ceee ste bas Selec cone cece 1 3t 
Wadthiof palate between last molar alveoli ...---.----. .-.---sscese\ecee see eseceeces cee « 4 7 
Penis HOSLOLLOmMGlEneuer Ol fiTst)MOlAL <2 -<cs ccceee eccces coeecs escccsisccses saemnnicecces 2 3 
AAMAVErROIaIAMOLer Ole tis biMOlA ys — ScVa2 3,55 oo5 wees ss) ee nee seb cae eiecc ees inctwasces cede 23 3h 
Eero HOstelionidiaMeLelion SeCONd MOlal..---- <<< c-oneecome cone cee ese sec vocencces asce 1} 3 
PIRADSMErAGdiamMetoror Second Molar. 2US.2.'52 2 -2eb sce las coon oes Cod cocbaccccase voccecce 2 3t 
Auiere-HOMbeniOr Ciamoeter Ot third MOTs -. <<< 3-20 sosewescesswcwcs ov eejeeesee ensciesce 1} 3 
REMNRGATN LAIN CLOMOM bE MITGm Olan 2 cs sscec sce -- 2 cascec sees ccae secsieecceascccicoccee 2 3} 
PUI CBENOIBOUN se Ser eater cine s[aots (eS sarenes cine Seac shbeenin Sas aides Does awteistsckaees | 2 34 
GeNuS STENEOFIBER E. Geoffr. 
* Stencofiber E. GEOrFROY, Revue Encyclop., 1833, —.” 
Paleocastor Luipy, Journ. Acad. Nat. Sci. Phila., 2d ser., v, 1869, 338. 
STENEOFIBER NEBRASCENSIS Leidy. 
Steneofiber nebrascensis Leipy, Proc. Acad. Nat. Sci. Phila., 1856, 89; 1857, 89. 
Chalicomys nebrascensis Lrrpy, Proc. Acad. Nat. Sci. Phila., 1857, 176. 
Palaocastor nebrascensis Lutpy, Journ. Acad. Nat. Sci. Phila.,2d ser., v, 1869, 338, 405, pl. xxvi, figs. 7-11 ; 
U.S. Geol. Survey of Wyoming, 1871, 363. 
The present species was first described by Dr. Leidy, in 1856, from 
specimens collected by Dr. Hayden from the Mauvaises Terres of the White 
River, Dakota. These specimens indicate an animal of about the size of 
Eucastor tortus. The species is thus far known from ‘‘a much mutilated skull, 
with the fragments retained nearly in their original position by a mass of 
included calcareous matrix. The greater part of the cranium is destroyed, 
as is also the nose and parts of the jaws, though all the teeth are preserved. 
A second specimen consists of portions of both jaws of an aged individual, 
badly mutilated and imbedded in a mass of matrix. The remaining speci- 
mens, from a third individual, consist of portions of both sides of the lower 
jaw and one side of the upper jaw, containing all the molar teeth, and freed 
from investing matrix.” 
