228 



COTTON-RAT. 



above described, it is obvious that the configuration of the triturating sur- 

 face, (occasioned by the folds of enamel dipping deeply into the body of the 

 tooth, in the second and third molar of the lower jaw,) accurately repre- 

 sents the letter S, which is reversed on the right side ; that bearing con- 

 siderable resemblance to the posterior tooth of the genus Spalax, and to 

 which also it has a slight affinity in the truncature of the inferior in- 

 cisors. The configuration of the intermediate molar of the upper jaw 

 may be compared to the form of the Greek letter 2, whence our generic 

 name." 



" In respect to its generic affinities, it is very obvious that its system of 

 dentition indicates a proximity to Arvicola, but the different arrangement 

 of the folds, and the circumstance of the molars being divided into radi- 

 cles, certainly exclude it from that genus. With respect to the radicles, 

 it resembles the genus Fiber ; but is allied to this genus in no other re- 

 spect." 



" We may further remark that the teeth of our specimen are consider- 

 ably worn, a condition that materially afliects the depths of the folds." 



Although the animal described below is the only species of Sigmodon 

 at present admitted into this genus, there are several well known, and 

 one undescribed, species, that we apprehend will yet be arranged un- 

 der it. 



SIGMODON HISPIDUM.— Say AND Ord. 



Cotton- Rat. 

 PLATE XXX.— Natural size. 



S. flavo fuscescens, infra cinereiun ; cauda corpore breviore ; auribus 

 amplis rotundatisque ; Tamise Lysteri magnitudine. 



CHABACTERS. 



Size of the chipping squirrel, {T. Lysteri;) tail, shorter than the body ; 

 ears, broad and rounded ; above, dark yellowish-brown ; cinereous beneath. 



STNONYMES. 



Marsh-Rat, Lawson'o Carolina, 1709, p. 125. 



The Wood-Rat, Bartram's Travels in East Florida, 1791, p. 124. 



