I. FROM THE TITANOTHERIUM BEDS.

Archæotherium scotti sp. nov.

In 1895 Professor Scott2 announced the discovery of the classic specimen now known as No. 10885 and mounted in the Geological Museum of Princeton University. This almost complete and unique skeleton (not "two almost complete skeletons" as mistakenly stated in the preliminary report) was found in the summer of 1894 by Mr. H. F. Wells in the upper Titanotherium beds in Corral Draw, South Dakota (whether in Pennington or Washington Counties does not appear), was secured by Mr. J. B. Hatcher and excavated by him May 11, 1894, and was referred by Professor Scott, in his announcement to the International Zoological Congress at Leyden, to Leidy's

FIG. 1. Archæotherium scotti sp. nov. Holotype, No. 10885. Three-quarter view of the skull and jaws from the left side, in the position in which it stands on the mounted skeleton, approximately one-sixth natural size. Drawn from photograph and the specimen.

2 W. B. Scott, "Compte-Rendu des Séances du Troisième Congrès International de Zoologie," Leyde, 16-21 Septembre, 1895. Leyde, E. J. Brill, 1896.

Elotherium ingens, "without paying much attention to the species," as he has since told me.

Elotherium ingens, as originally constituted,3 is a composite, comprising "fragments found in association with the fossils of Elotherium mortoni in the Mauvaises Terres, which appear too large to belong to this species, even making allowance for a considerable range in size." These were from the collection of Dr. Hayden, did not pertain to a single individual and were from unknown horizons. The first to be mentioned by Dr. Leidy is the "fore part of the lower jaw, in advance of the second premolars," which therefore becomes the type specimen of Elotherium (=Archæotherium) ingens. In the light of what is at present known regarding the larger entelodont species of the White River Oligocene, the various fragments included by Leidy with the type of ingens are specifically indeterminate, since the latter retains no teeth.

A suggestion of Mr. Troxell's, in a personal letter, first called my attention to the possibility that our Princeton specimen represented a new type and, on reviewing the subject, I agree with him that the mandibular fragment figured by Leidy in front view on Plate XXVII., Fig. 10, of the "Extinct Mammalian Fauna," copied here on a smaller scale as Fig. 4, differs both in size and structure from the corresponding part of the specimen monographed in detail by Professor Scott, for which I now propose the new name Archæotherium scotti (Figs. 1, 2, 3, 22), characterizing it as follows:

1. Very long and thick dependent malar process directed downward, forward and outward (the latter curvature probably intensified by crushing), with thin sinuous anterior margin and greatly thickened, round-edged, club-like posterior distal end, projecting so far below the anterior distal end of the process that the latter seems to contract in breadth a second time after a minimum of 88 mm, and a maximum of 114 mm. The greatest thickness of the enlarged end is 46 mm. The outer face of the process is convex transversely at the narrowest part, convex behind and flat in front at the widest 3 J. Leidy, "The Extinct Mammalian Fauna of Dakota and Nebraska," Jour. Acad. Nat. Sci. Phila., Vol. VII., Second Series, p. 192, 1869.

"The Osteology of Elotherium," Trans. Am. Phil. Soc., Vol. XIX., pp. 273-324. Pls. XVII., XVIII., 1898.

expansion and concave longitudinally, accentuated by crushing. Its front margin, at the point of greatest expansion, is in line with the posterior border of the orbit.

FIG. 2. Archæotherium scotti sp. nov. Holotype, No. 10885. Anterior mental process of the right side, seen from directly in front, one quarter the natural size.

FIG. 3. Archæotherium scotti sp. nov. Holotype, No. 10885. rior mental process from below, one quarter the natural size. proper orientation, the drawing should be held overhead in an sition and viewed from below.

Right anteTo get the inverted po

FIG. 4. Archæotherium ingens Leidy. Holotype. The front of the lower jaw showing the dependent processes. Copied from Leidy's figure, one quarter the natural size.

2. The zygomatic arch is 46 mm. wide at its narrowest part and the jugal process is very thin, and, while it extends to the front edge of the glenoid fossa, it takes no part therein and is not visible in side view, but only from below, as shown by the deep shading in Fig. 1.

3. Pï seems to have been double-rooted, judging from extremely slight indications of a median constriction across the alveolus, but it would be equally permissible to assume that the roots were conjoined, with merely a groove extending lengthwise between them. The empty alveolus measures 28 x 19 mm.

4. The anterior mental processes are very large and extremely broad at the base, anteroposteriorly (Fig. 3), but vertically the neck is only 20 mm. thick at the middle, thinning out to an edge front and rear. Distally, the process swells out to an oval bulb 61 x 36 mm. in diameters and curves outward, backward and upward (in part due to crushing). So far as can be determined from the figure of A. ingens (Fig. 4), the corresponding structure seems to have

been of uniform dimensions throughout, with a hemispherical termination. Some interesting differences in proportions appear in the following measurements given by Leidy, to which have been added the appropriate figures for the species described herein:

The posterior processes are long affairs with constricted neck and trilobate head, projecting outward and forward, the slope in the former direction being intensified by crushing.

To facilitate rapid comparison, the principal measurements are included in the table on page 114, appended to the description of A. wanlessi.

The drawing (Fig. 1), which has been traced from a photograph and corrected from the original. specimen, differs in many important respects from Von Iterson's plate in Professor Scott's memoir,5 especially in the delineation of the cheek flanges, the sagittal crest, the mental processes, and in the omission of teeth not present in the original, all of which greatly alter the contour of the skull as hitherto figured. As no drawings of the teeth have been published, the following notes are added to aid in making comparisons:

Upper incisors and canines had dropped out previous to fossilization. Pr is a small double-rooted tooth placed obliquely to the general direction of the tooth row and 11 mm. (left) to 18 mm. (right) back of the canine. It is well back of the canine on the right side, but has its anterior edge almost in line with the posterior border of the canine alveolus on the opposite side. The crown measures 25 mm. in long diameter on the alveolar border. P2 is represented by an empty alveolus 26 mm. back of p1. P3 is also lacking, and there is only a short space between it and p2, with the measurement of 4 Loc. cit., p. 192.

Loc. cit., Pl. XVII.

which the supporting framework of the mounted skeleton now interferes. P4 has its outer and back sides square, the inner rounded and the front deeply indented. On the anterior outer corner a prominence rises from the cingulum and the latter is present front and rear. Molars one and two are quadrangular, but too worn to show the crown patterns. Heavy cingula are present front and rear. In m3 the crown narrows in width posteriorly, the outer wall of the tooth converges inward, and there is a small posterior cingulum.

In the lower series incisors and canines are represented by empty alveoli, as is also pī, which, as indicated above, may have been either double-rooted or with a single grooved root. It is 14 mm. back of the canine and 16 mm. from the base of p2. The latter is a doublerooted tooth without cutting edges in its present worn condition. The back of the crown is broken, so I can not determine whether it is of uniform width throughout. P3 is long anteroposteriorly (52 mm. on alveolar border) in proportion to its width (20 mm.). The worn crown is convex on both sides and there are no cutting edges. There is a slight basal tubercle in front and a long sloping shelf behind, the worn area extending down over the posterior root below the enamel. The remaining teeth are in close series. P4 is heavier and thicker than the preceding and wider in front than behind. The sides are plane and there are no cutting edges on the worn crown which measures 39 by 22 mm. The molars are well worn, but retain traces of cingula front and rear. The anterior cusps seemingly were higher than the posterior. M3 has a prominent hypoconulid and the tooth crown is a little wider anteriorly than posteriorly. The other molars are of uniform transverse width.

II. FROM THE OREODON BEDS.

Archæotherium wanlessi sp. nov.

Type No. 12522, Princeton University Geological Museum, collecting locality 1015A2a, a splendid uncrushed skull with attached lower jaw and the first to fourth cervical vertebræ (Figs. 5, 6, 21) found by Mr. H. R. Wanless of the 1920 South Dakota Expedition on the 14th of last July in a large rusty nodule weathered out of the