1880.] 45 J [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 1 The monotreme-marsupial line have developed a number of loramina 

 in their own special way. 



(4) The Bodentia have chiefly developed those of the inferior part of the 

 squamosal bone, if any. 



(5) The Carnlvora commenced with but few foramina, and have obliter- 

 ated these on attaining their highest development. 



(C) The history of the Qnadrumana is identical with that of the Car- 

 nivora. 



(7) The Perissodaclyla present very few foramina in the lowest forms, 

 and did not increase them in the line of the Bhinoceridm. 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 foram- 

 ina is found in the specialized vegetable feeders, while the smallest num- 

 ber is found in omnivorous forms. 



I now give a synopsis of the distribution of the sinous foramina accord- 

 ing to the foramina themselves. The /. /. diploetiea, postzygomatica and 

 supratympanicum are not included, as their existence is restricted to the 

 few types already mentioned. 



I. No foramina. 



Homo, Troglodytes, Cynocephalus, Semnopitlieeus, Myceles, Cal- 

 ' lithrix, Ateles. 



Uncia, Hymna, Arctocephalus, Trieliems. 



Eleplias, Hyrax ; 



Sus, Phacoch&rus, Dicotyles. 



Lepm, Lagidium, Cercolabes. 



Cholcepus, Bradypus. 

 II. Postglenoid only. 

 a. Rudimental. 



Felis ; PJioca . 

 aw Developed. 



Chlamydophorus. 



Lemur, Ghirogalens, Tarshis ; 



Macacim. 



