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Show 10:3 ZOOLOGY OF THE VOYAGE OF THE DEAGLE. · f . p t Alta in Bahia Blanca, there is an f, sst Is from un a ' · Among the collectiOn ° 0 . . · nal of the Edentate order, m-f 1 1 d of a n·tgantlC anu iuteresting fragment 0 tle 1ea f' 0 1 . matic process of the left side. The . d ·t and part o t1e zygo · eluding the glenot cavt y, • . 1 .1. . 't flatness extent, and the absence . f' tl I ver JaW ex n nts, 111 J s . ' articular surface or le 0 ' • ' 1 1 . t : ·ties of this part of the Edental . . d the well-mnrkec c latac ens . of a postcnor n ge, . f' . 1. . the transverse, and two mches . . . It n asures two mches om mes m . . ·tlllctme. 1 e . d' . The commencement of the zygomatic . . l t ro Ilostenor tameter. f two lwes m t 1e an e - . f . 1 and a transverse diameter o t' l diameter o two me les, , process presents a vet Ica •. . t is slio·htl concave at its lower border, and ein·ht lines at the thtckestllpat t.t. I f tlleo cr~Iial llarietes, which is preserved, b The sma por ton o convex a ove. . n the oTeat extension and develop-exhibits the cellular structure conseqLtent upo o . l . t s has ah·eady · . . 1 . · . .- . this condition of the crama pane e • ' mcnt of the nasa a.u-smu~cs.' . . { t ·lulls of the larO'e extinct heen noticed in the descnptton of the more pm ec s ( o Edentata. NOTICE OF FRAGMENTS OF JUOLAR TEETH OF A MASTODON. Of the remains of this gigantic extinct Pachyderm, observed by Mr. Darwin. t S t ... pt., 1 · 11 Entre Rios and 011 the banks of the Tercero, the fragments of a an " e, ' ffi · t the teeth and portions of the skeleton which reached England, ar.e not su cwn to lead to a determination of the species; but sufficiently prov~ It t? have been nearly allied, if not identical, with the fllastodon angustidens. ot Cuv1er, and unq11 estionably distinct from the flfustadon g~f5Wileum of the United States. NOTICE OF TilE llEMAlNS OF A 'PECIES OF EQUUS, Fonnd associated with the extinct Edentals and Totrodou at Punta Alta, in Bahia Bla11ca, and witlt tlte Mastodon and Toxodon at Santa Fe, in Eutre Rios. The first of these remains ie; a superior molar toolh of the right side; it was e1nhedded in the quartz shingle, formed of pebbles strongly cemented together with calcareous matter, which adhered as closely to the tooth in question, as the correspotH.ling matrix did to the associated fossil remains. The tooth wa~ as completely fossilized as the remains of the Mylodon, Megatherium, and Scehdot~ere.~ aud was so far decomposed, that in the attempt to detach the adherent matnx, 1 1<'0SSIL 1\f AM MALIA. 109 iJccamc partially resolved into its component curved lamelJre. Every point of comparison that could be established proved it to ditfer from the tooth of the common Eqmts C(tbaltus only in a sliglJt inferiority of size . The sccoml evidence of the co-existence of the horse with the extinct Mammals of the tertiary epoch of South America reposes on a more perfect tooth, likewise of the upper jaw, from tbe red argillaceous earth of the Pampas at Bajada de Santa Fe, in the Province of Entre Hios.* This tooth is figured at Pl. XXXII. fig. 13 and 14, from which th anatomist can judge of its close correspondence with a middle molar of the left side of the upper jaw. rfhis tooth agreed so closely in colour and condition with the remains of the Mastodon and Toxodon, from the same locality, that J have no doubt respecting the contemporaneous existence of the individual horse, of which it once formed part, rrhis evidence of the former existence of a genus, which, as regards South America, had become extinct, and has a second time been introduced into t11at Continent, is not oue of the least interesting fruits of Mr. Darwin's pal~ontological discoveries. DE CJtiPTlON OF )lEl\lAl~~ OF lWDENTIA, INCLUDING THE JAWS AND TEETH OF AN EXTINCT SPECIES OF CTENOMYS. Tile fragment of the upper jaw, figured in Pl. XXXII. fig. 6, exhibits the first and second molar in situ, and the socket of the third and fourth molar, of a Rodent, which by tbe form and number of the upper maxillary teet!J is referable to the genus Ctenomys. The molars arc a little larger, the longitudinal groove on tlleir external surface is somewhat deeper, and thq last molar is relatively wider than in the existing subtcrrancous species,-the Tucutucu (Ctenornys Bmsiliensis, Bl.), of whose habits so interesting an acconnt is given in the description of the Mammalia of the present Collection (No. 1 V. p. 79). The form of the grinding surhtce of the first and second upper molar is shown below the fig. G, and three views of the second grinder are given at figs. 7, 0, and 9. The fragment of the lower jaw of the same fossil Rodent is figured at fig. 10 and 11. The long anterior incisor is relatively narrower than in tbe Ctenomys Brasiliensis. I have not had the means of comparing this fossil with the Ctenomys JJlogellanicus; but since it is probable that the Ct. liiagellanicus may not be specifically different from the Ct, • :1\'T r. Darwin l1a more p:uticularly described the circumsta.ncos of tho embedment of this tooth in his Joumal of Rc::~c':trchcs, p. 14·0, during tho Voyage of tho Dca.glc. |