FRESHWATER DOLPHINS. 
89 
on which the Whales feed. A specimen is exhibited in a small 
glass case at the north-west corner of the room. 
Nearly allied to the Sperm-Whale, but of much smaller 
size, is the Lesser Sperm-Whale, Cogia hrevicejos : the skeleton 
exhibited is from the neighbourhood of Sydney. 
The Beaked Whales, or Zipliiidcv, nearly allied to the Phy- 
seteridw^ resemble Sperm-Whales in having no upper teeth (or 
if present rudimentary and attached only to the gum), but differ 
in that the lower teeth, instead of being numerous, are reduced 
to one or, rarely, two pairs. They are situated either at the 
front extremity of the jaw, as in Zipliius and IlypeToddon, or near 
the middle, as in Mesoplodon. In one species of the last-named 
genus [M. layardi)^ from the South Seas, these teeth are much 
elongated and flattened, and in old animals (as in the skull 
exhibited) curve round and meet over the upper jaw, so as 
almost to prevent the mouth from opening. This disposition 
of the teeth has been found in so many individuals that it must 
be normal, and not, as at first thought, an aecidental peculiarity, 
though it is difficult to understand how it is consistent with 
the animal obtaining its food. 
The best-known member of this group found in the British 
seas is the Bottle-nose {Ilyperoddon rostraiu^^) . In the young of 
both sexes the bony crests on the upper surface of the skull are 
small, and in females they remain of medium size, but in males 
they gradually increase as age advances. This Whale is an 
inhabitant of the northern Atlantic, and, as it yields both 
spermaceti and oil equal in value to that of the Sperm-Whale, 
it is now the object of a regular “ fishery."’’ 
On the left side of the vestibule leadino- into the buildino- is 
O O 
a case containing the Freshwater Dolphins, or Platanistidcc. 
Among these are a model, a skeleton, and several skulls of 
the Dolphin of the rivers of India (Platanista gangetica), 
which has never been found in the open sea, but is exten- 
sively distributed throughout nearly the whole of the river- 
systems, not only of the Ganges, but of the Bramaputra and 
Indus, ascending as high as the depth of water permits. The 
eyes are exceedingly small and imperfect in structure ; and the 
creature appears to be quite blind. It feeds on small fish and 
