short way beyond its base, but immediately expands, and then gradually contracts,
the outline of the premaxillaries haying much the same contour as that of the
maxillaries,'
There are fewer teeth in the lower than in the upper jaw, there being
always two to three less in the former, and the lower are larger than the upper teeth.
The maximum number of teeth observed by me has been 17 in the upper jaw
associated with 14 teeth in the lower jaw on each side, and the minimum number
14 in the upper and 12 in the lower jaw, The number of teeth on the two sides of
the skull is liable to variation, 15 occurring on one side and perhaps 17 on the
other, and the same may take place in the lower jaw, subject, apparently, to a
maximum of 14 on both sides. In 0. brevirosti'is the teeth vary from 15 to 17
in the upper jaw and from 12 to 14 in the lower jaw. One individual has ^ ”
and another * ** % ™
The premaxillaries have each one tooth near the external margin of their tips,
and in this respect Orcella resembles Orca. In the foetus in which the teeth had
their points still covered by the gums the diameter of a tooth did not exceed
0"-07, whereas the same tooth in the mother had a diameter of 0"'20. The teeth
are rather sharply conical, and their crowns are slightly inclined inwards, but
with use they become perfectly flat. In an adolescent 0. brevirostris the teeth
are unworn, but in an adult they are much worn away, especially the eight
hindermost teeth, but the remaining portions of these teeth have much greater
diameter than the corresponding portions of the same teeth in the adolescent.
The hyoid apparatus has the usual delphinoid character.
Conclusion.—The form of the skull of Orcella, the character of its teeth, the
relation of its ribs to the vertebral column, the features of the latter generally,
the well ossified sternal ribs, and the presence of a dorsal fin,—all indicate it to be
a member of the family Delphmidce. The sub-division of the Delphmidce into
natural groups, however, as has been remarked by Professor Elower1, is by no means
easy, and we must either make as many sub-families as there are genera or group
them together into one family. Professor Reinhardt2 also, in remarking on the
systematic position of Pseudorca, contended that to regard Orca as a division among
the toothed whales of more than generic worth, as a group or family by themselves,
as had been suggested by Eschricht, was neither sound in itself nor indeed supported
by any defensible reason, and what was true of Orca in this respect was equally
applicable to Globicephalus, Grampus, Dagenorhynchus, Phoccena, 8fc. Dr. Gray,
however, followed an entirely different course, as he elevated Grampus, Globicephalus,
and Orca into as many distinct families, and the Delphmidce he sub-divided into
five tribes, but as Professor Elower further remarks, the genera so blend one into
the other that it is difficult neatly to define their distinguishing characters, and each
new discovery of a Delphinoid Cetacean seems to lend more weight to these opinions.
1 Trans. Zool. Soc. 1869, vol. vi. p. 114.
* Oversigt. over Kong. Danske, Vidensk. Selsk. Eorhand. 1862; Transl. Bay Soc. 1866, p. 218.
The present genus well illustrates the truth of these remarks, as it is at ofice
apparent that it has certain undoubted resemblances to Globicephalus, Grampus,
Orca and Pseudorca, whereas at the same time it so differs from each of them that
the only course left is to refer the two species to a distinct genus. The term Orcella,
however, is unfortunate, as in their external features they are not diminutive
representatives of the killers, as they have neither high fins to their backs nor very
broad pectorals*
This Cetacean type was originally regarded by Oweni as a Phoccena, but it has
not the compressed teeth distinctive of that genus, from which it also widely differs
in the characters of its vertebral column and in its external features generally.
Dr. Gray2 at first considered it to be so nearly allied to Orca as only to merit subgeneric
rank to the killers. I t is, however, as I have just mentioned, remarkably
distinct from these Cetaceans, as the dorsal fin, instead of being high and in thé
middlpi of the back, is low and placed behind the middle of the body. Orca is also
distinguished by having extraordinarily large pectoral fins, nearly as broad as long,
whereas, in Orcella, the pectoral flipper, although proportionally much broader than
in Globicephalus, is only about half as broad as long. The pectoral limb, ais a whole,
is also proportionally considerably longer and narrower than in Orca. This is due
to1 the greater length of the bones of the arm and those of the metacarpus and
phalanges, which'in Orca are relatively much less developed than in Orcella. In
the manus also other differences present themselves, as the second and third fingers
of Orcella are much longer than those of Orca, whereas the fourth and fifth are
rather shorter. Orca also’ is distinguished from Orcella by its much more powerfully
built skeleton with considerably fewer vertebrae, there being only a maximum
of 58 in it, to a maximum of 68 in Orcella. The cervical region of Orca, moreover,
has generally four or five vertebrae anchylosed, whilst in the two species of Orcella
the atlas and axis only amalgamate. Eurther, in the Killers and Ca’ing whales
the ribs are transferred to the transverse processes at the pth dorsal, whilst in
Orcella the transference does not take place until the 8th. In its conical teeth,
which are about the same number as in Orca, Orcella resembles the killers, and,
as pointed out by Reinhardt,3 the breadth of the upper jaw in Orca is produced by
the maxillaries and not by the premaxillaries, as in Globicephalus, and in this
feature: its skull resembles Orca.
Dr. Gray, in his last work on the Cetacea,4 separated Orcella front Orda, which
he elevated into a distinct family, the Orcadce ;6 elevating Orcella to generic rank
and placing it alongside Pseudorca, which he regarded as the type of a tribe of
Delphmidce. Pseudorca, however, has- a much more depressed head than Orcella,
which is intermediate in this respect between Orca and Globicephalusl The dorsal
11. c.
8 Cat. Seals and.Whales, 1866, p. 285.
3‘ l. d; p. 198.
4 Suppl. Gat. Seals and:Whales; B; M. 187-1, pi SOl
. . 6 I. o. p. 86.