426 ZOOLOGY. -° 
ceptible of but little expansion. There are from thirty-two to forty-seven. 
teeth on each side according to the age of the individuals. These conical, 
acute, and a little crooked teeth are slightly dilated on their middle. They 
are larger on the middle of the maxillaries than at their extremities, but are as 
simple in their roots as in their crown. When the jaws close, the teeth of 
one jaw lodge themselves in the intervals left between those of the other. The 
use of such teeth is to retain prey rather than to masticate it, for they swallow. 
their food entire. The nesarnak or nisarnak of the Greenlanders (D. turszo) 
is another species of this genus, known also under the name of bottle-nosed 
whale. It is quite rare, being seldom seen near the shores. It differs from | 
the common dolphin by a shorter snout and a smaller number of teeth, the 
form of which is obtuse. The body is short, the snout flattened above, the 
color entirely black with the exception of a small portion of the abdomen, 
which is whitish. Nearly forty species of Delphinus are described or men- 
tioned in Cuvier’s ‘‘ Histoire Naturelle des Cétacés,” many of which are 
still very doubtful, as they were never examined, but only seen in open sea 
from vessels. We would only mention one species more, D. peronii, from 
the south of Van Diemen’s Land, as it is deprived of a dorsal fin, the only 
one of the genus as it would seem. The lower part of the body and the 
snout are completely white, a peculiarity which caused Peron to bestow 
upon it the name of D. leucorhamphus. Several extinct species of Del- 
phinus are described as peculiar to the old world. Lately another species 
has been detected in the State of Vermont, which differs from all others. 
The genus Jiza resembles closely the dolphins proper by the general 
appearance of its external form and proportions. The snout is, however, 
more elongated, the pectoral fins broader, and the dorsal fin represented by 
a mere elevation of the skin. But the most prominent character is derived 
from the teeth, which are nipple-shaped. Only one species is known of this 
genus, inhabiting the rivers of the province of Moxos, South America. 
This is the £. boliviensis, which is said to attain a length of twelve feet. 
The angle of the mouth extends as far back as the eyes. The mouth itself 
is linear and only a little arched posteriorly. The skull is depressed, the 
snout thin, nearly cylindrical, and obtuse at its extremity. The number of 
teeth ranges from one hundred and thirty to one hundred and thirty-four; 
_ sixty-six or sixty-eight in the upper jaw, and sixty-four or sixty-six in the 
lower. Their surface is rough with deep interrupted grooves. On the 
front of the jaws the teeth are conical and crooked, whilst the others are 
thicker. 
The genus Platanista comprehends one single species from the river 
Ganges, representing with the genus Inia the family of dolphins in the 
fresh waters. The chief character of the genus consists in the narrowness 
of the jaws, with thin and prominent crests projecting forwards from the 
maxillaries on each side of the blow-hole. The Pl. gangetica reaches 
seven feet and more in length. The head is short and rounded; the beak 
Jong, thin, narrow, without lips, dilated upon its extremity. There is a 
rudimentary dorsal fin; the pectorals are very large, and the caudal nearly 
even. _— : 
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