44 



Male.* 



5-5 

 Molares r— 



Female.t 



2-3 

 Molares — 



Male, 3 



2-2 

 Molares — 



Cranium. 



Length of the cranium 



Prom the occipital crest to the upper border of 



the nasal aperture 



Length of nasal aperture 



Breadth of ditto 



From the lower border of the nasal aperture to 



the end of the intermaxillary bone , 



Breadth of occiput 



Smallest interspace of the temporal ridges 



Greatest distance between zygomatic arches 



Greatest distance between postorbital processes 



of the frontal bone 



Lower Jaw. 



From the condyle to the lower part of the sym- 

 physis 



From the condyle to the base of the ascending 

 ramus , 



Breadth of ascending »*a»w2w 



Length of dental (molar) series , 



Length oi Aa^xw^ symphysis 



Breadth of ditto 



From outside of one condyle to that of the other 



From the condyloid to the coronoid process 



ni. lin. 



13 11 



4 10 



4 



2 6 



6 

 2 



2 

 4 

 2 

 6 

 2 





 10 

 

 6 

 2 

 3 

 o 



in. lin. 

 14 8 



5 

 5§ 

 2 9 



10 



6 

 2 

 2 

 5 

 2 

 6 

 2 



7 



4 



3 



10 



6 

 10 

 

 

 G 

 6 

 7 



in. lin. 

 14 6 





 

 



811 

 10 



211 

 4 



11 3 



6 6 

 3 

 2** 

 5 2 

 2 3 



7 

 2 7 



" The short and thick neck, fin-like fore-legs, want of hind-legs, 

 caudal tegumentary fin, smooth, naked, and almost hairless integu- 

 ment, are all modifications of external form, by which the Dugongs 

 and Manatees are adapted to play their part in the waters : but the 

 kind of part which they are to play in that element depends on or- 

 ganic characters which mainly if not exclusively reveal their true 

 affinities. Now we have seen that the whole of the internal struc- 

 ture in the herbivorous Cetacea differs as widely from that of the 

 carnivorous Cetacea, as do their habits : that the amount of varia- 

 tion is as great as well could be in animals of the same class, exist- 



* Deciduous and permanent tusks in place ; the first molar, left side, 

 lower jaw shed. Outer wall of sockets of permanent tusks entire. 



\ Deciduous tusks shed and their sockets obliterated ; the points of the 

 permanent tusks protruding from their sockets : the shallow cavity at their 

 base exposed by the absorption of the wall of the socket at that part. 



I Sockets of deciduous tusks obliterated, permanent ones protruded to 

 the usual extent and worn by use : their sockets entire. 



§ This dimension increases as the intermaxillary bones are lengthened 

 in the antero-posterior direction. 



II The increase of this dimension is due to the greater development of 

 the lower part of the intermaxillary bones in correspondence with the sexual 

 condition of the tusk. 



^ This dimension of course diminishes with the increased development 

 of the temporal muscles consequent upon the fitness of the tusk for use. 



«* The increasing breadth of the last molar compensates for the loss of 

 the small anterior molars. 



