90 
WHALE LOOM. 
crustaceans, which it gropes for with its long snout in the 
muddy water at the bottom of the rivers. The blowhole, as 
may be seen in the model, is a single slit, placed length- 
wise, and not transversely to the head as in most Dolphins, and 
the back-fin is merely a low ridge. The skull has on the 
up})er surface a pair of large, compressed, bony crests, over- 
arching the aperture of the nostrils and base of the beak, and 
nearly meeting in the middle line above. The jaws are 
exceedingly long and narrow, and armed with numerous. 
Fig’. r)C. 
Tlie Dolphin (DelpJmms delphis). 
Skull of the Dolphin. 
slender, pointed teeth, which undergo curious changes of form 
as life advances, the cast of the beak of a very old individual 
exhibiting the form assumed by the teeth at this stage. 
In the .■5ame case are the skeleton and some skulls of another 
freshwater Dolphin, Inia geofroyensis^ from the Upper Amazon 
and its tributary streams, and also of a species, Pontoporia 
Jjlainvillei, from the estuary of the Rio de la Plata, of very 
small .size, with long and slender jaws and the most numerous 
