(EXTRACTED FROM THE TRANSACTIONS OF rHE AMERICAN PHILOSOPHICAl SOCIETI ! 



ARTICLE XX III 



A Memoir on the extinct Dicotylinae qf America. By Joseph Leidy, M. D. Read May 21, 



1852. 



The genus Dicotyles, so far as our knowledge extends, appears always to have replaced 

 the genus Sus upon the American continent. 



The two existing species of Dicotyles inhabit all the tropical parts of America, and even 

 extend into Texas. The larger is the D. labiatus, the other the D. torquatus. 



I have not been able to find any authority who gives the distinct osteological characters 

 of the head of the two species except Dr. Rengger in his Naturgcschichtc der Siiugethicrc 

 von Paraguay, p. 329. 



De Blainvillc in his Osteographie, Article Sus, has given three views, in Plate V., of the 

 skull of D. labiatus, which he has named D. torquatus, although he has represented an 

 undoubted entire skeleton of the latter in Plate III. 



The differences observed between a specimen of the head of D. labiatus and five speci- 

 mens of the head of D. torquatus, preserved in the collection of the Academy of Natural 

 Sciences, arc as follow: 



The narrow portion of the cranium, produced by the approach above of the temporal 

 fossa?, is not only relatively but absolutely longer in D. torquatus than in D. labiatus. 



The lower portion of the face is relatively broader in the latter, produced by a promi- 

 nence commencing on the inner side of the infra-orbitar foramen advancing and gra- 

 dually increasing to the canine alveolus. The prominence slopes outwards from its upper 

 part to its lower margin where it ceases abruptly, and overhangs the anterior premolar 

 alveoli and the edge of the hiatus in advance of the latter, so as to conceal them in 

 viewing the skull from above. It encroaches on the transverse diameter of the infra- 

 orbitar foramen, and thus gives it a semi-oval form. It is hollow, and accommodates 

 a large portion of the inferior scroll of the turbinated bone. In D. torquatus the promi- 

 nence docs not exist, and its position is occupied by a concavity proceeding from the in- 

 fra-orbitai foramen, which in this species is oval. Moreover, the latter foramen in D. tor- 

 quatas is above the third premolar, while in the other species it is above the first true 

 molar. 



