Cope.]

[Feb. 6,

Ursus, Arctotherium and Hyanodon; postglenoid, mastoid and postparietal.

Enhydrocyon and Temnocyon; postglenoid and postparietal only.

FIG. 2.-Temnocyon coryphæus Cope, Lower Miocene of Oregon; one-half natural size. PP, postparietal foramen.

Archalurus, Dinictis, Pogonodon, Hoplophoneus and Macharodus (cerebralis); postglenoid and postparietal only.

Procyon, Nasua and Passaris; postglenoid only.

Canis, Vulpes and Urocyon; postglenoid only.

Viverra, Mustela, Putorius and Mephitis; postglenoid only.

Felis (domestica); sometimes a minute postglenoid only; sometimes none. Hyana, Uncia, Cynælurus; no foramina.

PROSIMIÆ.

QUADRUMANA.

Hapale; postglenoid and postsquamosal.

Cebus; postglenoid and postparietal. The latter is on the suture of the parietal and squamosal bones; in Hapale penicillata it is entirely within the squamosal bones.

Ateles, Callithrix, Mycetes, Semnopithecus and Cynocephalus; no foramina.

Macacus; a small postglenoid.

Troglodytes niger, gorilla; a closed fissure, but no foramen postglenoid

eum.

Homo; no foramina in sixteen North American Indians examined of the Klamath, Bannock, Crow, Sioux and Cheyenne tribes. One postglenoid on one side in a South Australian. One or two mastoids are more usual, being found in a good many specimens of all races. They are rarest in Hottentot negroes.

СЕТАСЕА.

Balana, Beluga and Monodon; no foramina.

SIRENIA.

Halicore and Manatus; a huge mastoid only.

1880.]

[Cope.

HYRACOIDEA.

Hyrax; no foramina.

PROBOSCIDIA.

Elephas; no foramina.

PERISSODACTYLA.

In this order the number of the foramina ranges from very few to many.

FIG. 3.-Aphelops megalodus Cope, Loup Fork of Colorado; one-sixth natural size; showing postparietal foramen.

Rhinocerus, Aphelops; post parietal only.

Skulls of Aphelops megalodus (Fig. 4) and A. fossiger (Fig. 5) from behind; onesixth natural size; showing absence of mastoid foramen.

Tapirus; post parietal and a huge mastoid.

Anchitherium, Hippotherium, Protohippus and Equus; postparietal, postsquamosal, postglenoid and supraglenoid. In the last three genera PROC. AMER. PHILOS. SOC. XVIII. 105. 3G. PRINTED MARCH 6, 1880.

Cope.]

[Feb. 6,

the vessel issuing from the postsquamosal, grooves the petrous bone, leaving it at a point near that usually occupied by the mastoid foramen. In the second and last genera, and probably in the third, the sinous canal is protected by a bony crest in front, throughout its entire length.

ARTIODACTYLA.

Great diversities are found in this order, especially between the suilline and ruminant divisions. In the former, with the exception of the Hippopotamide, there are no foramina; in the Ruminantia they are more numerous than in any other order of the class. The Ruminantia are, like the equine Perissodactyla, characterized by the presence of the supraglenoid foramen; to this the Camelida and some others add the mastoid. The. Tragulina must be excepted from this rule, for they have nothing but the postglenoid.

Omnivora.

Sus, Dicotyles and Phacocharus; no foramina.

Hippopotamus and Charopsis; postglenoid, postsquamosal, mastoid and a rudimental supraglenoid.

Tragulus; postglenoid only.

Ruminantia.

Oreodon; postparietal and mastoid. In one specimen of O. culbertsoni from Colorado, I find a minute supraglenoid on each side; in other specimens it is wanting.

Poëbrotherium; postparietal, postglenoid; mastoid; a small supraglen

FIG. 6.-Skull of Procamelus occidentalis Leidy, Loup Fork of New Mexico; one-fourth natural size; showing supraglenoid foramen, SPG.

Procamelus, Camelus, Auchenia; postglenoid, supraglenoid and mastoid. Bos; postglenoid and supraglenoid only.

Antilocapra; postparietal, postglenoid, mastoid, and a large supraglen

oid.

Giraffa; posi glenoid, supraglenoid, postsquamosal and mastoid.

Oreas, Ovis, Cervus; postglenoid, supraglenoid, postsquamosal, postparietal and mastoid.

1880.]

[Cope.

From the preceding the following conclusions may be derived : (1) The sinous foramina furnish valuable diagnostic characters, and may, with proper limitation, be used in systematic definition.

(2) The primitive condition of the various mammalian orders appears to have been the possession of a limited number of these foramina.

(3. The monotreme-marsupial line have developed a number of toramina in their own special way.

(4) The Rodentia have chiefly developed those of the inferior part of the squamosal bone, if any.

(5) The Carnivora commenced with but few foramina, and have obliterated these on attaining their highest development.

(6) The history of the Quadrumana is identical with that of the Carnivora.

(7) The Perissodactyla present very few foramina in the lowest forms, and did not increase them in the line of the Rhinoceride. In the line of the horses an increase in their number appeared early in geologic time, and is fully maintained in the existing species.

(8) In the Omnivorous division of the Artiodactyla, time has obliterated all the sinous foramina. In the Camels an increased number was apparent at the same geologic period as in the history of the horses (White River or Lowest Miocene), and has been maintained ever since; while the existing Pecora present a larger number of the foramina than any of the class of Mammalia.

The only relation between these structures and the habits of the species concerned that can now be traced is, that the largest number of the foramina is found in the specialized vegetable feeders, while the smallest number is found in omnivorous forms.

I now give a synopsis of the distribution of the sinous foramina according to the foramina themselves. The f. f. diploëtica, postzygomatica and supratympanicum are not included, as their existence is restricted to the few types already mentioned.

I. No foramina.

Homo, Troglodytes, Cynocephalus, Semnopithecus, Mycetes, Callithrix, Ateles.

Uncia, Hyana, Arctocephalus, Trichecus.

Cope.]

Mustela, Putorius, Mephitis; Canis. Vulpes, Urocyon; Viverra.
Procyon, Nasua, Bassaris.

Lagostomus and Geomys.

III. Subsquamosal only..

Phascolarctos.

IV. Postsquamosal only.

Ornithorhyncus, Tamandua, Blarina, Condylura, Scalops.

V. Postparietal only.

Rhinocerus, Aphelops.

VI. Mastoid only.

Halicore, Manatus.

VII. Postglenoid and subsquamosal only.

Hystrix, Hydrocharus, Capromys, Calogenys, Sciurus, Haplodontia, Neotoma, Hesperomgs, Mus, Arvicola.

VIII. Postglenoid and postsquamosal only.

Erinaceus.

Масториз, Нуpsiprymnus.

Hapale.

IX. Postglenoid and postparietal.
Chiroptera sp.

Temnocyon, Enhydrocyon;

Archælurus, Dinictis, Pogonodon, Hoplophoneus, Macharodus.

XVI. Supraglenoid, postglenoid and mastoid.

Procamelus, Camelus, Auchenia.

XVII. Supraglenoid, postglenoid, mastoid, postparietal. a. Supraglenoid small.

Poëbrotherium.