482 Transactions.— Zoology. 
shown for distinguishing under a new specific name the Blackfish of the 
Pacific, when it appears on the Californian coast. The Black fish has the 
same habits and range as the Sperm Whale, frequenting the subtropical seas 
in large schools, and occasionally, like the great Cachelot, extending their 
migrations to temperate latitudes, and even doubling Cape Horn. As there 
is now generally admitted to be only one species of Sperm Whale common 
to all seas, the division of the Pilot Whales into distinet species should 
require very definite proof, so that the skeletons which have been trans- 
mitted to various museums in Europe and America will enable an accurate 
comparison to be made with the northern forms, and settle this interesting 
question of distribution. 
The only differential characteristics are to be found in obscure shades and 
patches of lighter colour, and in the number and form of the teeth, which 
are notoriously mere individual characteristics among this group of Cetacea, 
the teeth showing a marked tendency to disappear wholly, or in part, in old 
individuals. Among the school of Pilot Whales under review some have 
only nine and others twelve teeth in the upper jaw, while the usual number 
in the lower jaw was ten. 
The great individual variety in the number and position of the teeth 
that are either absorbed or are lost early in life, becomes, however, still 
more marked among the Ziphioid Whales, and has led to the temporary 
establishment of species and even generic distinctions in numerous in- 
stances, 
The state of the bones proved that the animal was of mature age. 
The skull is 28 inches along the floor, with an extreme width behind 
the orbit of 19 inches. Of this total length the beak occupies exactly one- 
half (28 inches). It is broad, flat, and slightly bent down on the top. Its 
upper part is formed by an expansion of the callous premaxillaries, which 
are slightly depressed in the middle line between the notches, and are 
separated throughout by a wide groove. The entire vertex of the cranium 
is formed by the nasal bones, which are very prominent. 
The lower aspect of the beak is formed entirely of the maxillaries, the 
palatine bones only showing as a narrow band between the maxille and 
the pterygoids, and the premaxillaries only showing in this aspect as & 
small area on the top of the rostrum. 
The tooth series occupies the borders of the maxille for half their 
length, and show ten alveoli with raised margins, but some are almost 
obliterated. 
The lower jaw, which is rather slender, has nine alveoli in a groove, 
which is wider at the symphysis and narrow behind. The symphysis only 
extends back as far as the fourth tooth from the top. 
