422 Dr. H. Woodward — On the Fossil Sirenia. 



They were observed by bim to be gregarious in tbeir babits, slow 

 and inactive in their movements, and very mild and inoffensive in 

 their disposition. Tbeir colour was dark brown, sometimes varied 

 with spots. The skin was naked, but covered witb a very thick, 

 bard, rugged, bark-like epidermis, infested by numerous parasites. 

 One of these, the Cyamus Bhytince, bas been described and figured by 

 Prof. Brandt.i 



When full-grown, they are said to have sometimes attained a lengtb 

 of 35 feet and a weight of 3 or 4 tons. 



Like most of tbe Herbivora, they spent the chief part of their 

 time in browsing. They were not easily disturbed whilst so occu- 

 pied, even by the presence of man. They entertained great attach- 

 ment for each otber ; and when one was harpooned, the others made 

 incredible attempts to rescue it. They were so heavy and large that, 

 Steller records, tbey required 40 men with ropes to drag the body of 

 one to land. 



If we compare the extinct Bhytina witb tbe existing forms of Sea- 

 Sirens, we shall see that it approaches most nearly to the Dugong 

 (Halicore), which when adult has only one pair of incisors left in the 

 upper jaw, and two (rarely three) molars on eacb side above and 

 below, making 14 teetb in all. 



But adding the milk-dentition, we have in Halicore: — 



1— 1 3—3 



Milk-dentition ] 3—3 3—3 



[ Incisors. Molars. ^_^ 



Permanent teetb ) 2^1 ^tz^ rarely oHq 



0—0 2—2 



The teeth in Halicore are more or less cylindrical ; tbe incisors, in 

 their form and wear, resemble those of the Hippopotamus. The last 

 molar is compressed laterally, giving the crown a figure-of-eigbt 

 shape ; but there is no distinction into root and crown. The sum- 

 mits of tbe crown are tuberculated before wearing ; afterwards they 

 are flattened or slightly concave. 



After the milk incisor-teeth of Halicore are shed, their alveoli, 

 along the anterior balf of tbe mandible, are covered over with a thick 

 horny epithelium, which serves in the adult as a bruising-plate in 

 lieu of the anterior teeth, as is the case in Bhytina. 



In Manatus senegalensis the only milk-teeth present are the 



incisors, ~ , which speedily disappear; but the molars amount to 



T-j — —=48 in all. The upper molars have two ridges and three 



roots ; the lower mandibular series have an additional posterior 

 ridge or talon, and only two fangs. 



The teeth drop out in front, and are renewed from behind as in 

 the Proboscidea. 



This extreme variation in the number of the teetb from 2 (milk- 

 incisors) in Bhytina, to 48 teeth in Manatus, is exactly paralleled in 



' " Cynmus Rhytinm." Mem. Acad. St. Petersb. 1871, vol. xvii. No. 7; and 

 Ann. and Mag. Nat. Hist. 1872, pp. 306-313. 



