338 STELLER’S SEA-COW CHAP. XI 
complete skeleton. The skull is lke that of other Sirenia, with 
the down-turned premaxillary region. But the nasal bones, lost, 
or at least rudimentary, in recent forms, are well developed; the 
likeness of ancient to living forms in this respect being exactly 
paralleled by the Zeuglodonts, when compared with recent Whales. 
The vertebral centra exhibit distinct epiphyses, which have dis- 
appeared in living Sirenians. The cervical vertebrae are seven, of 
which the second and third are occasionally fused. There are 
nineteen pairs of ribs, and there are three lumbar vertebrae. 
The sternum consists of three separate pieces. There is a 
rudimentary femur. 
The recently-extinct Steller’s Sea-cow, belonging to the genus 
Rhytina, was a huge beast, seen in the flesh up to nearly the end 
of the last century. It frequented the shores of Bering’s Straits. 
Its remains occur in the peat on the shores of those seas. It reaches 
a length of some 20 to 30 feet. The external characters were 
much like those of other recent Sirenians. The nostrils were above 
the fore part of the snout, the latter being truncated and obtuse. 
The tail was of the Cetacean pattern, and thus like that of Halicore. 
The head of this Sirenian was small, and the teeth had entirely 
vanished save for the apparent existence as transitory structures 
of two small incisors in the upper jaw. The absence of teeth 
was compensated by the presence of a horny palate for the 
trituration of the sea-weeds which constituted the food of Steller’s 
Sea-cow. The fore-limbs seem to have possessed no nails, but 
were covered at the extremity with short, bristly hairs, no doubt 
serving the purpose of keeping the animal moored in safety to 
the slippery beds of Fucus upon which it browsed. 
There are nineteen pairs of ribs. The vertebrae of the 
cervical region are the customary seven, and the centra are thin 
and plate-like as in the Cetacea, the animal being thus short- 
necked like those marine creatures, 
