Cope.] O [^IHay ]6, 



a well-preserved lower jaw of a Mastodon, which presents both rami, and 

 both the last true molars, and the entire symphysis. In the collection of 

 the Ecole des Mines I saw a palate with the second and third true molars 

 of both sides in place, and the superior incisor teeth, or tusks. Other 

 fragments of jaws, with numerous isolated molars, were seen in these col- 

 lections and in that of the college of the city of Tolnca.* 



From these specimens it is clear that the high valleys of Mexico were 

 inhabited by a trilophodont mastodon, with a short decurved toothless 

 symphysis like that of the Eleplias j^rimtgenius, and with a band ot 

 enamel on the superior incisor tusks. The molars have the characters of 

 those of the 3Iastodon andium of authors, and are of about the same size. 

 The cross-crests are divided at the middle line only, and one half wears 

 into a trefoil, while the other half wears into an oval, transverse to the 

 long axis of the crown. The unworn crests are obtuse and not serrate ; 

 .and there are no accessory tubercles besides those forming the lateral lobes 

 of the trefoils. The size of the ramus and of the teeth is about that of the 

 M. angustidens, and smaller than that of the M. humboldtii. The last in- 

 ferior and last superior molars have but four cross-crests and a small heel. 

 This I verified on several specimens. 



A comparison of this species with those described, yields the following 

 results : In the charact er of its molars it is identical with the M. andium, 

 and difiers from the M. liumboldtii in the characters which distinguish the 

 two species, as pointed out by Gervais.f That is, only one-half of each 

 cross-crest wears into a trefoil, and the size is inferior. But it cannot be 

 identified with the Tetrnbelodon andiurn, because, according to Falconer,:}: 

 that species possesses a long massive deflected beak containing an incisor 

 tooth. 11 It is true that the specimen figured by Laurillard in D'Orbigny's 

 voyage dans I'Amerique Meridionale, PI. x, does not display a long beak 

 and tusk, although the symphysis is much more pronounced than in the 

 present species. But that plate is made from a drawing, and may thus 

 be of doubtful authority. If correct, it may represent the female, or, as 

 Falconer suggests, the young of the T. andium. The last inferior molar 

 figured by Dr. Leidy, 1. c, and formerly referred to a species under the 

 name of Mastodon sJiepardi, has the character of the corresponding tooth 

 of the Mexican species under considei'ation. The plate does not, how- 

 ever, represent the specimen satisfactorily in one respect. The trefoils are 

 not sufficiently distinct, on account of the faint representation of their 

 basal lobes. These nearly block up the cross valley, a fact not to be de- 

 rived from an examination of the plate, but which is clearly seen in a cast 

 preserved in the museum of the Philadelphia Academy of Natural Sciences. 



* For the opportunity of examining the museum of tliis Institution I am 

 mucli indebted to its President, Dr. Villada. 



t In Castelnau's Expedition, 1855; Recherclies sur les Mammiferes Fossiles de 

 I'Amerique Meridionale, p. 14. 



J Palpeontological Memoirs, ii, pp. 22fi, 274. 



II The lower jaw figured by Falconer, Mem, i. p. 100, from Buenos Ayres, as M. 

 audium is clearly ^1/. humboldtii. 



