Vol. 6] 



Merriam: Notes on Desmostylus. 



411 



In the large size of the nasals and maxillaries Desmostylus 

 is more primitive than any other form referred to the Sirenia. 

 The situation of the anterior narial openings seen here is dif- 



Fig. 10. Desmostylus, sp. Superior view of anterior region of the 

 skull, X %• Miocene of Japan. Fr, frontal region; Na, nasal; Mx, max- 

 illary; Pmx, premaxillary ; Up I, upper incisor. (After Yoshiwara and 

 Iwasaki ). 



Pig. 11. Desmostylus, sp. Lateral view of a portion of the skull with 

 the lower jaw, X %. Miocene of Japan. Pmx, premaxillary; Mx, max- 

 illary ; Or, orbital region ; Pm, fourth upper premolar ; M 1 , first upper 

 molar; M'-, second upper molar; Mel, mandible; Lo I lt first lower incisor; 

 Lo I 2 , second lower incisor. (After Yoshiwara and Iwasaki.) 



ferent from that in other forms of this order. The other char- 

 acters of the skull are unfortunately not clearly shown in this 

 specimen. 



Fragments of ribs and vertebrae referable to sirenians have 

 been found in the middle Tertiary of California, and some or 



