452 



MONOORAPna OP NOUTU AMBBICAN UODENTIA. 



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This species, so fur ns these specimens iiulicntc its character, appears to 

 reseml)K! the genus Steneqfiber, from the lower Pliocene formr.*ion of Saint- 

 derand-lePuy, France, both in the general form of the skull and in its den- 

 tition. So great is this resemblance that Dr. Leidy at tirst referred it to 

 that genus, which Kaup has regarded as identical witii Chalicomys. The lower 

 jaw in Steneojiher, says Leidy, is unknown, and adds that that of Pa/teocaslor 

 is quite unlike the lower jaw in Chalicomys. The structure of the molars in 

 Clia/icoinys dilfers greatly, as shown by Gervuis's tigures,* from that of Steneo- 

 Jilier, and G'-ofTroy, Gervais, and others regard the two forms as generically 

 distinct. In Valaocastor, the structure of the molars is very similar to what 

 is seen in the figures of the molars of Steneojiber. In respect to the skull, 

 Leidy also observes that the "forehead presents the same triangular form and 

 l)ropoi-tionate size" as in Steneqfilyer. "The temporal fossae", he continues, 

 "appear to have had the same form and proportional capacity. They were 

 Separated in the same manner by a long sagittal crest, extending forward upon 

 the frontal bone. The cranium, just back of the forehead, was equally con- 

 stricted. The external auditory passage formed a short, oblique canal, with 

 its orifice directed outward and backward in the same manner. The palatal 

 region, likewise, had the same form and construction, and the infra-orbital for- 

 amen held the same relative j)osition as in Steneq/ilwr viciacensis. The inci- 

 sors in both jaws arc proportionately as long and strong as in the Beaver, 

 and they have the same fi)rm." Dr. Leidy adds that they also strongly 

 approach in form those of the Beaver. 



The molar teeth in " PalcEocnstor" differ very greatly in ntructure from 

 those of cither Cantor, Eucastor, or Trogontherium, more resembling, appar- 

 ently, as do also those of Steneof,ber viciacenuvs, those of some members of 

 th(! DtUiyproctidcE. The skull also differs greatly in form from that seen in 

 liiese genera in consequence of the much greater constriction above of the 

 int(!rorbital region. Ilencc ^'Palaocastor", if really belonging to the tiunily 

 Castoridtr, probably differed very much in general structure from the existing 

 Beavers, and has its nearest ally in the geims Steneq/iberf of the Miocene 

 epoch of Europe. 



*Zool. et pali^ont. fraiif., plates i, viii, and xlviil. 



i Qorvais Riiyn, "Lew genres Ckalicomyii, Kaiip, et Sleaeoftber, K. Ocnfr..8ont<!videmnientdola memo 

 Iribu que leg CnstorH" (Ziiol. ut pa16iint. franv., p. 20), to wliioti group tliey have been generally referred 

 by Bubeeqnont writers. Mr. E. R. Alston, however, in. bla recent memoir " On tbc Classitloation of the 

 Order Ulint" (V. Z. 8., lt)70, pp. (U-'J8), gives Imlh Chahcomyt of Kaup and /'o/(R><»«*or of lioldy among 

 tbo " more doubtful fossil geni'ra " of the funilly Catlorida; as fvolt as the genera Palmmjt and CktMui 

 of Kaup, and tbc genus DvgoHlkeriiim of Fiscber (nut TrogoHthiriim of Oweu, -^ Uiobrolicm, Pomel). 



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