86 Transactions.— Zoology. 
Art. XV.—WNotice of a Variation in the Dentition of nap dei hectori, 
Gray. By James Hector, M.D., F.R.S. 
Plate XV.A. 
[Read before the Wellington Philosophical Society, 13th October, 1873.] 
Tuts specimen is only a fragment of the lower jaw, but the portions preserved 
afford sufficient characters to determine the genus, and to show that it differs 
from any described specimen, and also throw some light on the little known 
subject of the dentition of the Ziphiide. 
The posterior portion of the left ramus from the condyle to the symphysis, 
and the middle portion of the right ramus, is all that remains. About two 
inches of the surface of the suture enable the angle of divergence of the jaws 
to be determined, and, therefore, the width of the cranial articulation. 
Opposite the commencement of the symphysis (sy) was a deeply excavated 
alveolus, which, in the left side, contains a triangular tooth (¢). The dental groove 
has evidently been open and deeply excavated in the back part of the jaw, and 
where broken off on both sides, it appears as if it was expanding to form a 
second tooth chamber (#). 
~ Left Ramus.—The condyle is very feeble, but not more so than in 
M. hectori, to which the jaw bone is very similar except as regards the 
teeth.* The articular surface is 1:3 inches long and 0-3 inch wide, and 
situated above the middle of the posterior border, which is convex externally 
and 4 inches in length. On the inside the posterior third of the bone is 
deeply excavated, very thin, and on the outer surface shows one large 
inferior and a small superior ridge. The upper margin is compressed, thin, 
and elevated to form a blunt angle, behind which the dental groove begins at 
6 inches from the condyle. The inferior margin is rounded, but with a blunt 
keel-like ridge, and slopes up rapidly, reducing the width of the ramus from 
3:3 inches posteriorly to 1:5 inches in its middle third. This middle third is 
solid, compressed, and obliquely turned like a ploughshare, so that at the 
symphysis the dental grooves are on the outer side of the jaws 2 inches apart, 
and separated by a flat area formed by the symphysial processes, which are 
conjoined to form the terminal portion of the lower beak. The width at the 
condyles was probably 8 inches ; engin = y кур, 12:5 inches. 
Tooth. —The chief interest of thi tition, as in this it differs 
from the type specimen both in the ATE and character of the tooth. In the 
first respect it resembles the original type of the genus M. sowerbyensis, as the - 
tip of the tooth (/) is exactly opposite to the posterior end of the symphysis (sy). 
Behind it the dental groove, though distinctly visible, is quite closed, but it 
* Trans. N.Z. Inst., Vol. IL, p. 27; Vol. IIL, p. 125; Vol. V., p. 167. 
