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MONOORAIMia OF NOIITII AMBltlCAN IJODENTIA. 



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(fGNKRic ciiAKH. — Rkiill willi tlic (lurtuil outliiic nonrly stniiglit; iVuntal 

 region Hat or licprrssiiil ; |)UHtorl)ilals triangular at base, with a lung, Hprend- 

 ing, (lociirvi-d point; zygomatic archer mudiTatoly nxpandoti, not \vi(l(>ning 

 an<l diverging posteriorly ; grinding-teeth rather small, the transverse and 

 untero-posterior diameters altont equal, and the molar scries very nearly 

 parallel*, occipital and interparietjil crests well devel ihmI (in old nge) ; ante- 

 orbital foramina subtrinngular, widest beluw, but nut tnruwn outward. Size 

 largo; body thick-set, broad, depressed ; cheek-pouches small; tail rather 

 short, bushy, not llattened ; ears small ; nail of |M)IIcx broad, flat, or wanting ; 

 pelage with long coarse hairs and thick under fur. Coluratiun generally ycl- 

 luwish-gray, without either distinct spots or stripes. 



The gt'uus Arctomijx differs from Cynoinyx in many quite import.ml 

 features. In Aiclomyit, the dorsal outline of the skull is straight, or nearly 

 so, instead of highly arched, ns in Cynoiin/n; the zygomatic arches arc rela- 

 tively smaller, and reach their greatest expansion near the middle instead uf 

 at their posterior border; the grinding-teeth are small, in nearly porallel series, 

 nnd differ widely from those of Cynomys in shape and in mode uf inseitiun. 

 In Arctomys, the molars are inscrte<l nearly vertically, as in the true Squirrel.i; 

 in Cynomyn, their insertiun is quite obli((UP. In Aiclomyn, the triturating 

 surface of the crowns is nearly square, but the inner burder is somewhat 

 narrowed, so that tiie teeth of the same series touch each other by their 

 crown surfaces for only two-thirds of their transverse breadth ; in Cynomys, 

 the transverse breadth of the crowns is twice that of the onlero-j^iosterior, 

 and internally the teeth are so much narrowed that they abut clof;ely fur only 

 half their transverse breadth, leaving internally deep openings between the 

 teeth. In Arctomys, the p.iliite is bruad and scarcely narrower at the last 

 molnr tlian anteriorly, while in Cynoinyn the palate is rapidly and greatly 

 narrowed posteriorly. Ilcncc Arctomys «liffers very widely from Cynomyn in 

 respect to the size, form, and position of the molar teetli ond the form of the 

 bony palate.. In all these points, Arctomys is more Sciurine than is even 



onltes, genree ut caiidcea qui aoiit iioinniiSa dans cetouvruge [DoDtii d«a Hnnimiftres], avvc une Byno- 

 nymio latino", occurs thu fulloniug:— 



"&4. Mamiottea, orctomya. Oiuel. 



" Murmoitu dcs AI|H'8, Arctomyi alpimis. Lion. 

 " Marniotte dii Canuda, Arctomjit cmpelro. I'all." 

 Wbnt be means by " Arvtomyi tmpvira I'uU." is crrtiiiiily not clear, s.nve no ori||iual dcBCTi|itiou of 

 Palla«'K tmi>rlra biul at tbiH datu (IH'.fi'i) uppuared, vxcrpt l'ullu8'i>urti(lnul account of bit MuiemiHstra. 

 Babinu'H Aniomya rt»i>ctra (IS'2'i) is Are-omyt movaz. \l Cuvirr ba<t s|)«cini«ns of tbe "Marniottu da 

 Cunudu', bia " Arvlomyt rm^fra I'hII.'' in doubtless also icferublu to A. m/iiajc. 



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