476 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1907. 
whale (fig. 20) contains large, conical teeth, about 25 on each side, 
while the upper jaw (both maxille and premaxille) is toothless. 
The sperm whales are allied to the beaked whales, which are repre- 
sented by the bottle-nosed whale, yperoddon. This whale is at least 
10 meters (323 feet) long, and is remarkable from the fact that it has 
only one, or at most two, pairs of teeth, in the front of the lower jaw. 
All the other teeth have disappeared, or are represented only by 
minute, stunted denticles in the gums, which are never cut. 
The third family of toothed whales embraces two small river 
dolphins, one of which (Pontoporia, or Stenodelphis) (fig. 4) lives at 
Fic. 4. 
j OT shed fiw, 
ms FOB: 
Pa rea ae 
oS ae pal Rwy San, Hi Ale ~ 
hed ee ae F a3 yi (Poa. = (AO PP OE, 
ae oA (al? Gata sts Saeco 
2 a 
Leis 
Nin WS nt Na dds 
MiGao Ae MGs. Be 
Fig. 4.—River dolphin (Pontoporia or Stenodelphis blainvillei Gervais) from the mouth of 
the Rio de la Plata. About 7s natural size. 
Fig. epg. of porpoise (Phocsena spinipinnis Burmeister) from the Argentine coast. 
About 3 = natural size. 
Fic. 5B w of the dorsa! fin of the same animal from above. In the divisions of the 
skin (Ceeeteldenn) are seen bony protuberances, which are the remains of the extensive 
dermal armor in the ancestors of this animal. About % natural size. After H. Bur- 
meister. 
the mouth of the Rio de la Plata, and the second (/nia) in the 
Amazon. It comprises also the white whale, or beluga (Delphinap- 
terus), which reaches a length of 4 or 5 meters (13 to 164 feet), and 
the narwhal.¢ 
The enormous tusk of the male narwhal, which reaches a length of 
3 meters, was looked upon in earlier ages as a miraculously powerful, 
“The white whale and the narwhal are usually placed in the family Del- 
phinide, or the true dolphins, but in a separate subfamily.—F. W. T. 
