PERFECT SKELETON OE RHYTINA GIOAS. 465 



large rivers ; but they never venture far away from the shore. 

 Their food consists entirely of aquatic plants, upon which they 

 browse beneath the surface, as the terrestrial herbivorous mammals 

 feed upon the green pastures on land *. 



When Steller came to Behring's Island in 1741, the Sea-cows 

 pastured in the shallows along the shore, and collected in herds like 

 cattle. As they fed, they raised their heads every four or five 

 minutes from below water in order to breathe before again descending 

 to browse on the thick beds of sea- weed which surround the coast. 



They were observed by him to be gregarioas in their habits, slow 

 and. inactive in their movements, and very mild and inofi^ensive in 

 their disposition. Their colour was dark-brown, sometimes varied 

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

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



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

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



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

 time in browsing. They were not easily disturbed whilst so 

 occupied, even by the presence of man. They entertained great 

 attachment for each other ; and when one was harpooned, the others 

 made incredible attempts to rescue it. They were so heavy and 

 large that, Steller records, they required 40 men with ropes to drag 

 the body of one to land. 



Fossil and Recent Allies of Ehytina. — In Miocene and Pliocene 

 times Sirenians were abundant over a large portion of Europe. 

 Many of these are referable to the genus HalitJierium, first described 

 by Kaup from the Miocene of Hesse Darmstadt. 



HalitJierium resembled the Dugong in its dentition (fig. 3), 

 having tusk-like incisors in the upper jaw, though these were not so 

 largely developed as in Halicore. The molar teeth were |- or f , the 

 anterior teeth were simple and single-rooted, the posterior teeth of 

 the upper jaw with three roots, and those below with two roots, and 

 with enamelled and tuberculated or ridged crowns, in all which 

 points they resemble the Manatee more than the Dugong. The 

 anterior molars were deciduous. 



The pelvic bones are better developed than in existing Sirenians 

 (fig. 2) ; there is also a rudimentary styliform femur. They were 

 therefore less specialized than their modern representatives (Plower). 



In Prorastomus (Owen) from the Tertiary of Jamaica, the denti- 

 tion is very remarkable ; for we have present at one and the same 

 time, clearly difi'erentiated — incisors g^, canines ^, premolars 

 14, and molars |=^=48 teeth. 



5 — 6' 6 — o 



"'' Mr. William Carruthers, F.R.S., F.G-.S., informs me that the large sea- 

 weeds called Laminarice grow in water at or just below low -water ; they are 

 nutritious and are eaten by animals. They abound in the North Pacific Ocean. 

 Puprecht, in his account of the Algaj of the North Pacific, records eight species 

 of these large weeds growing in the Sea of Ochotsk, on the shores of Kamts- 

 chatka, and the north of North America. He adds : — " When I went to see the 

 Coniferous trees at Monterey, California, last autumn, I was surprised at the 

 magnitude and quantity of the Fuel and Laminarice thrown up on the coast." 



