PROF. W. H. FLOWER ON THE GENUS MESOPLODON. AIT 
Berardius hectori, Gray, Annals & Mag. N. H. ser. 4, vol. viii. p. 117 (1871). 
Mesoplodon knoxi, Hector, Trans. New-Zeal. Inst. vol. v. p. 167 (1873). 
Hab. Titai Bay, New Zealand. Very young; length 9' 3", 1866 (Know and Hector). 
6. M. eray1, Haast, Proc. Zool. Soc. 1876, p. 7. 
Oulodon grayi, Haast, P. Z.S. 1876, p. 457". 
Hab. New Zealand. 
These six species do not differ greatly in size, and present a close family or, rather, 
generic resemblance ; but still there are certain cranial and dental characters by which 
the skulls can readily be distinguished. 
The most easily recdgnized of these are :— 
a. In some species there is a deep lateral longitudinal groove at the base of the 
rostrum, commencing posteriorly in a blind pit below the tubercle of the maxilla 
situated in front of the anteorbital notch, and bounded above and below by sharply 
defined prominent ridges, both formed by the maxilla. This groove characterizes 
M. grayi and M. densirostris. No trace of this groove, but a prominent ridge instead, 
which gives a wide base to the rostrum, as seen from above or below, exists in 
M. bidens, M. ewropeus, and M. hectori. The groove is slightly developed in MV. layardi, 
which in this respect presents an intermediate condition. 
b. The relative position of the foramina for the exit of the facial branches of the 
second division of the fifth nerve appears to afford constant distinctive characters between 
certain of the species. The principal foramina are in two pairs :—1, the larger or more 
external, situated in the maxilla, and often double, corresponding to the infraorbital 
foramen in man (Plate LXXI. mf’); and, 2, the smaller and nearer the middle line, 
situated in the premaxilla (pf). The latter are rather in front of, or on the same level 
with, the maxillary foramina in W/. bidens, M. europeus, M. hectori, and M. layardi, and 
placed decidedly on a posterior level in I. densirostris and M. grayi. 
c. The constant presence of a row of small teeth in the upper jaw is said to dis- 
tinguish MW. grayi from the other species, though, as will be discussed presently, this 
can scarcely be considered of generic importance. 
d. The position of the large tooth in the lower jaw, whether close to the apex of the 
‘ In the notice of this paper in the Proceedings of the Zoological Society, 1877, p. 684, for 
Sea ap MV RLESY NASP silois =) ye present memoir,” read :— 
7. M. haasti, n. sp. 
Hab. New Zealand. 
Known only by a portion of a cranium in the Museum of the Royal College of Surgeons. 
8. M. australis, n. sp. = M. hectori (Gray). Hector, Trans. New-Zealand Inst. vol. vi. p. 86, and vol. vii. 
p. 362. 
Hab. New Zealand. 
A complete skeleton, now in the British Museum, described in the present memoir. 
