XII.] 



SIRENIA. 



199 



have skulls constructed on a very peculiar type, though with 

 some affinities both to the Ungulata and the Proboscideia. 

 Many of the special modifications are adaptations to their 



FMx 



nxO 



Fig. 64.— Section of the skull ot an African Manati {Manatits senegalensis), \ 

 PMx premaxilla ; Vo vomer; j\lx maxilla; Fr frontal; ET ethmoturbinal ; 

 ME mesethmoid ; Fr frontal ; Pa parietal ; Sg squamosal ; SO supraoccipital ; 

 £jrO exoccipital : /"^r periotic ; ^O basioccipital ; 7> tympanic; yJ^ alisphenoid ; 

 BS basisphenoid ; PS presphenoid ; Pt pterygoid ; PL palatine ; Mx maxilla ; 

 cp coronoid process of mandible ; cd condyle ; a angle ; J symphj'sis ; sh stylo- 

 hyal ; bh basihyal ; th thyrohyal. 



aquatic mode of life, and it is in these alone that they 

 present any resemblances to the Cetacea. 



The skull of the African ^Manati {Alanatus senegaknsis), 



