Even when it opens so far as to allow the mandible to pass behind the apices of the canines, there would appear to be some risk of the latter's becoming caught on the point of one or the other canine, and forced to remain open, causing early starvation.. Such may have been the fate of the fine individual of the S. neogaus, Lund, whose skull was found in Brazil by Lund, and which is familiar to us through the figures of De Blainville, etc.

DREPANODON Nesti. (Macharodus Kaup).

This genus as understood by most authors, belongs to the later Miocene and Pliocene, and has had numerous representatives in Europe and Asia. No species has as yet been found in America. Some of the species described by authors are only known from fragments, so that much remains to be ascertained as to the prevalence among them of the characters I have assigned to the genus and family. Those given are derived from the two species best known, the D. cultridens and D. megantereon, which have been readily obtained from the descriptions and figures of authors.

It is difficult to ascertain the number of European species. Pomel's catalogue is generally cited, and this is, with some subtractions and additions, the basis of the list already given.

SMILODON Lund.

Besides the family characters already given, this genus differs from the Nimravide in two other important respects. In both points it differs also from such existing members of the Felida with which I have been able to compare it. In both S. fatalis and S. necator, the posttympanic process of the skull is coōssified with the postglenoid, thus closing the auricular meatus below. It thus differs from other Felide as the genus Rhinocerus differs from various other members of Rhinocerida. The second point has been indicated by Prof. Gervais. There is no epitrochlear arterial canal, such as belongs to cats and Nimravide generally. This I have only verified on the S. necator.

This genus represents in America the Drepanodons of the Old World. The known species belong to the Pliocene period, and were the cotemporaries of the gigantic sloths and Glyptodons, which at that time ranged over the entire American continent. Their powerful limbs terminated by immense claws, bespeak for them exceptional force in striking and tearing their prey, and the long compressed canine teeth are well adapted for penetrating the

tough hides and muscles of the large Edentata, which were doubtless their food. There are known two species of large size from

the Pliocene of South America, and probably two species from North America. A figure of the skeleton of the S. necator Gervais accompanies this paper. It is a copy of a lithograph taken by Prof. Burmeister from a specimen in the Museum of Buenos Ayres. The second known skeleton, found by M. Larroque near to the village Areco, a few miles west of Buenos Ayres, is in possession of the writer. Lateral and inferior views

of the skull of this individual, one-third of the natural size, are represented in figures 13 and 14.

FIG. 14.-Smilodon necator, one-third natural size. Inferior view of skull Fig. 12.

This specimen is the one on which the late Prof. Gervais based his determination of the species (Comptes Rendus, 1878, June), but which he had not described at the time of his death. The species is about the size of the lion, and of the most formidable character.

A fragment of a maxillary bone containing a sectorial tooth found in Texas was referred to an extinct cat, by Prof. Leidy, under

the name of Trucifelis fatalis. As it possesses a second anterior basal lobe of the superior sectorial, it is doubtless a Smilodon. I am confirmed in this opinion by the characters presented by an important specimen sent me by G. W. Marnock, who obtained it in Southwestern Texas. It consists of

that portion of a cranium, which is posterior to the orbits, and represents an animal of the size of the S. necator, or of a large tiger. The positions of the foramina and the conjunction of the posttympanic and postglenoid processes are as in the S. necator. When more of this species is known, it will doubtless be found to be our largest sabre-tooth.

Among the remains obtained by Charles M. Wheatley from a cave on the Schuylkill river, in Pennsylvania, which I described in 1871, there occurred a part of the canine of a sabretooth. Hoping to obtain better specimens, I did not include it in the published lists. Having established the existence of the genus Smilodon as a contemporary of the sloths during the Pliocene period in North America, it becomes probable that the species of the caves is also to be referred to it. The canine in question has lost most. of its crown. It is of smaller size than that of either of the three species previously mentioned, and its basal portion is more compressed. This compression is a marked character, and I refer to it the name Smilodon gracilis, by which the species may be known. UNCIA Gray (Cope emend.).

FIG. 15. Smilodon necator; humerus of specimen Figs. 12, 13, from front, one-third natural size. Mus. Cope.

Extinct species of this genus have been found in the late Miocene and subsequent deposits in India, Europe and North America. It is distinguished from the

true Felis by the round form of its pupils. This can only be observed in the living species, so that some correlated index of it must be used in determining the genus from skulls. This Dr. Gray shows is seen in the small size of the orbits, which are always less than those of the species of Felis.

Fragmentary remains from the Loup Fork formation of Nebraska and the Pliocene and Quaternary of Mississippi and California have been described by Leidy under the names of Felis augustus, F. atrox and F. imperialis. Dr. Leidy suggests that there may have been two species, the one (F. augustus) characteristic of the Loup Fork epoch, and F. atrox, the second, belonging to a later period. The Uncia augusta was intermediate in size between the U. onca and the tiger, while the Uncia atrox was, according to Leidy, larger than the lion or tiger. It represents in America the Uncia spelea of the European caves, and should be carefully compared with that species.

:0:

TWIN LAKES
LAKES AND TEOCALLI MOUNTAIN, CEN-
TRAL COLORADO, WITH REMARKS ON THE
GLACIAL PHENOMENA OF THAT REGION.

ONE

BY F. V. HAYDEN.

NE of the most interesting localities in Central Colorado, is the Twin lakes. These lakes are situated at the point where Lake Fork issues from the Sierra Madre, or Wasatch range, into the short valley which opens into the Upper Arkansas. At no distant period this point, with its surroundings, will form one of the most popular and desirable watering places in the West; already every available spot in the vicinity has been purchased for the purpose of erecting summer houses. The elevation of the lakes is 9357 feet above sea level. Some of the loftiest peaks in Colorado are in full view of the surrounding hills. Massive mountain, Mt. Elbert, Harvard, Yale and Princeton peaks, rise to heights of over 14,000 feet. The massive granite mountains on every side, are among the most rugged and picturesque in the Rocky Mountain region.

During the survey of this region in 1873, under the direction of the writer, these lakes were carefully sounded, and their greatest depths were found to be respectively seventy and seventy-six feet. These are formed in basins, as it were, which