40G Bulletin American Museum of Natural History. [Vol. XXVII, 



from the Perissodactyla; that their ancestry is probably not to be sought in 

 the known Condylarthra; and that the principal peculiarities of the skull 

 and dentition and especially of the limbs and feet were already foreshadowed 

 in the Creodonta, from unknown Basal Eocene members of which they may 

 possibly have sprung. 



Affinity with the Carnivores is also indicated by certain features of recent 

 Artiodactyls. In the cerebrum the Sylvian fossa is surrounded by 3 con- 

 centric gyri, the sylvian, suprasylvian and marginal (Weber, 1904, p. 126). 

 The ossicula auditus are very different from those of the Perissodactyla and 

 are distinguished by the frequent recurrence of the broadly laminate form 

 of malleus which prevails among the fissipede Carnivora (Doran, 1879, p. 

 421). 



At the same time the Lemuroid-Insectivore facies of the skull of Dicho- 

 bvnc and other Eocene Artiodactyls suggests the possibility that not all 

 Artiodactyls have been derived from a pro-Creodont source. 



XI. The Sirenia. 



Historical Notes. 



A summary of the early history of discovery is given by Gervais (1835, 

 p. 331). 



According to Ray (1693, p. 194) the Manatee was described by the 

 Spaniards as Manati "quod posterioribus pedibus careat." Ray placed the 

 Manatee after the Walrus under the "Quadrupeda vivipara unguiculata, 

 multifido, carnivora majora, capite longiore, seu Caninum genus." 



By nearly all the earlier systematists the Sirenia were affiliated with the 

 Cetacea. De Blainville (1816), the great innovator in classification, boldly 

 separated them from the Cetacea and placed them with "les monodelphes 

 Ongulogrades " in a grand division " anomaux" of that order. Later (1834), 

 relying upon the numerous resemblances between the Proboscideans and 

 Sirenians he associated these two grou])s in "les Gravigrades," a group of 

 superordinal rank. 



Later authors simply assigned the Sirenia separate ordinal rank and 

 gradually gave up the idea of close relationship with the Cetacea. 



The most notable of the numerous known fossil Sirenia are: (1) Ilali- 

 therium from the Oligocene of Europe, described in detail by Kaup in the 

 first half of the nineteenth century (1838-1855). Kaup (1855, pp. 9, 10) 

 at first regarded this genus as an ally of Dinotherium, and like de Blainville 

 pointed out the resemblances between Proboscidea and Sirenia, regarding 

 the Proboscidea are representing the "Primatentypus" of the Sirenia. 



