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Show 220 EXPLORA'l'lON OF 'rOE CANONS OF THl~ COLORADO. perfectly well-discriminated species, the early ]inks between which have entirely disappeared, leavincr the forms ns stable us possible. Thomomys is still in a transition-stage at present. Setting aside tho peculiar T. clusius, described as new beyond, all tho known forms of that genus are still only incompletely separated. and the links binding them are plainly before our eyes. rrhe genus appears to be making into u number of species, but the procc s is still far from completion. In talking over t his singular difference in the nutund hi tory of the e two closely-allied genera with Professor Bairn, he threw out a suggestion, which, pe rh np~, may account for the facts. While we have no means of knowing which is the older of the two genera, so as to compare the rnt.cs of' progress they respectively made in developing their speeies, yet we mny fhirly infer, upon geographical considerations, that Geomys hns been longer about it than Thomomys. Geomys, though found to n certain longitude we tward, is C5 ent.ially a fcmn of Eastern N ort.h America, extended thence to Central America, and it is presumably upon older grounrl than the late deposits in the West, where Tlwrnomys occurs. In i he cases of many mammal and birds of this coni inent, it will be rccollcctecl there is a perfectly stable cn~ teni species of n genu which in theW est is repre~ented by a numbet· of "varieties.'' Junco, Melospiza, PasSf''rella, Picus, arc good illustrationt::. But be the explanation what it may, there is no douht about the filCt that Geomys has made itself into five or six firm spr.cies before Thomomys has succecrled iu turning out more than one or two. With these few observations by way of introducing the specie~, I shall proc~ed at once to give an account of them, rc:servi 11g many detail which c.ontnbuted ~o the result of my investigat iou, as well as all general consi(lcro.tlons respeetmg the family, for publication in a different connection. GENUS GEOMYS. (emend. ex Raf.) !JftttJ, sp. SnAw, et al., 1. c. infra. Cricetus, 11p. DF.Sllf., et al., 1. c. inj1·a. Geomys, RArr., Am. Month. Mag. ii, 1817,45. Viplostoma, RArr., op. et Zoe. oit. (ebn.r. plorumq: inopt.), !ICC Hrcn SaccopltoruB, KuuL, Dcitr. 18'.20, 65. · PBcudoiJtoma, SAY, Loug'l! Exp. R. Mts. i, 1f,'!!3, 406. Atoomys, LtCU'f., Auhand. Dorl. Acn.d. 1822-'3, 1825, 20. OOUES ON GEOMYS AND 'fBOMOMYS- G. BUltSARIUS. 221 GEOMYS BUHSAlUUB, (Shaw) H.ich. Mus bui'Bat'ius, SuA~, Linn. Tmua. v , 1800, 221, fig. 8; Gon. Zool. i l, 1801, 100, pl. 138 (tho plate elot\l'ly sltow1:1 t lto gmovcd incisors; tho pouches 1uo ovor tcd).-Mnc., Am. Jouru. Sci. lv, 1~22, 183. CricettiB bul'sari1t81 Dlr.SM., Nouv. Diet. cl' Hi~:~t. Nat. xiv, - , 177; E ney. Moth. Snppl. pl. 10, f. 4; Mnmm. ii, 18~:l, p. 312 (lmi'Bal'ens).-F. Cuv., Diet. Se. Nn.t. xx, - , 257.- DI>:Si\foUL., Diet. CIIU!S. viii, - , 37.-Gnu•'F., Anim. Kiugd. iii, 1~Z7, l3H, pl. - ; v, 1827, 23{), No. 012. SaocopltontB btu·sm·ius, Kum ., UoiLriigo, 1820, 65.-Frson., Syuop. 1827, 304. Pse• dostoma btt1'11rwius, SAY, Lo ug't~ Exp. U.. Mts. i, 182:.1, 406 (burBaria).- IIAIILAN1 Fu. Amer. 1~20, 1G3.L1r. ss., Mt•n. 18<J7, 2G0.-000MAN1 Am. Nat.. Hi1:1t. ii, 18:l1, 90 (bttrsarium).-DrcKAY1 N.Y. l!'o. i, Hl42, 9:l.-Aun. & lhcn., Q. N. A. i, 1849, 332, pl. 44. Ocomysf bursal'ius, RICn., F. U. A. i, 1829, 20:l; Rop. Brit. Assoc. for 1836, v, ld37, 1G6 (nee Gmy). .AscontJJB bursm•itts, EYo. & Glm"V ., Voy. :Favorite, v, 1 :m, ~3.-Scnllsz , Syu. i i, 184G, 132.-Gmu., Odout ug. r,:J, pl. 23, f. 8. Gc·umys bm·sarittB, Wooon., Znfli and Cnl. U.. 1853, 50.-PARVIN, Aon. Rop. Smit.lts. Inst. for· 1854, 1855, ~!J3 ( ltt•bi ti:!).-Kir.NN., 'l'mnl:!. 111inois Agric. Soc. for 1853-'4, 1855, 580.- Bo., M. N. A. 1857, :372, pl. 22, lig-. 1 a-11, and pl. GO, fig. 2 a -g.-MAXIM., Arcll. Nu.tnrg. 1861, - ; Vurz. U.uiso N.-Am. SiLng. 1802, 147.-Giclut., Cat. Bones Br. Mus. 1802, 223.-LJCIDY, Proo. Acad. Nu.t. Sci. P lt ilu.. Hlli7, U7 (~:~Ic n ll from loess of Mi~:~sotll'i).-AMJts, Bull. Acad. Minnesota, 1, 1874, iO. GcontyB (Saccophorus) bursarius, GmBEL, Si.i.ug. 185(1, 529. " f Mus ludo11icianttB, 0 1m, Gnthl'io's Goog. 2d Am. od. ii, 1815, 292. (Not dotormiua.ulo.)" f Diplostom.ajMca, RAir., Aru. Mouth. Mag. ii, 1817, 44.-DrcsM., Mn.mru. ii, 1822, 315.-LJtss., Man. 18~7, 201. f Diplostoma alba, HAF., Am. Month. Mag. ii, 1817,44 ~ n.luiuo).-OESM., Mnmm. ii, 1822, 315.- LESS., Man. 1B27, 201. · .'iaccophorusf a/bus, F rscn ., Synop. 18:l7, 305. 7 Ocomys cincrous, RMr., Am. Month. Mag. ii, 1817, 45. Mus Baccatus, MITCH., N. Y. Mod. Rupos. x xi, 1821, 249. Lhcomys canadtm.Bi8, L lCIIT., Abh. Aend. Wiss. Bol'i. 11"!23, l:J, flg.- BRANTS, Muizon, 1827, 24.-WAON., Snppl. Schroll. iii, 1843, :183; Abh. K. llnior. Alcad. MUnch. xxh, 1846, 327, fig. (skeleton). Gcomylt canadcltBiB, Lite., Proc. Acacl. Nat. Sci. Pltila. vi, 18:>2, 158. Ueomys oreganen.sis, L~tc. , P roc. Acad. Nat. Sci. Plti ln.. vi, 1852, JGO (no prounuility t hat. the assigned locality i1:1 COI'l'Oot). OeomytJ bret:i()('pB, Do., P roc. Aon.cl. Nn.t .. Sci. Plliln. 1855, 334; M. N. A. 1857, 378, pl. 52, f . 2 a-g.-GEnR. Cut. Uooos Dr. Mns. 1802, 22:3. Cnuada Rat, Stu w, ll. co. Canada Ponchcd Bat, RrCIIAIIDS0:-\1 l. c.-Auo. & BAcu., l. c. IIamtJtcr dtt Cauada, D lcSi\t., l. c. Pscudostome a bourse, L1css., l. o. DiplostolltO ,bl'lm, D. blanclt.c, DltSl\f., LESS., ll. oo. Canadia1t Daml!lcr, Onuwnn, Z. c. Oo.fT. r, 1'aschc11maus, SCDlNZ, l. c. Punched Rat, Sa11d Rat, Camas Rat, Poolcl't Gopher, Salamandel', Vulg. Oaufre, French ( whonco E n glit~h "t;ophor," ancl Gorman " gotlor"). Quicl Gcomy1 dmmmondH, R10 11., Hop. Brit. Assoc. v, 1837, 157 (Asoomys dt·ummondii npud Wagn., Suppl. Scbrcu.), spocio1:1 iudct. donti llmlprim. uisu lcati~:~ f DrAGNOSlS.-Su pcrior incisors bisulcute, with a fine sharp groove along the inner margin, and another much larger bisecting the remaining plane surface. Cheek-pouches ample, extending to the shoulders. Hands (inclurling claw ) longer than feet. rrail and feet hairy. Pelugc soft, sleek, mole-like. Color dull reddish-browu, murldy-gray or hoary beneath, the basal port.i11D |