340 MR. W. H. FLOWER ON THE OSTEOLOGY OF THE SPEKM-WHALE. 
articular facet for the head of the rib, gradually becomes more distinct, and ultimately 
forms the main transverse process, serially continuous with those of the lumbar region. 
We have thus in the hinder part of the dorsal region of the Sperm-Whale a perfect 
repetition of the characters of the cervical vertebra of ordinary Mammals, as far as the 
transverse processes are concerned, an upper one springing from the arch, a lower one 
springing from the body, and uniting at their extremities so as to form a complete bony 
ring. 
In this important character of the spinal column Hyperoodon agrees with Physeter ; 
and this appears to me one of the most striking points of affinity between these two 
genera. In the skeleton of the Hyperoodon in the Hunterian Collection in the 
College of Surgeons, upper transverse processes are regularly developed from the arches 
of the dorsal vertebre as far as the seventh, but cease in the eighth. The lower pro- 
cesses arising from the body begin in the seventh, which has thus two processes, which 
(in this immature specimen at least) do not meet at the ends; but the bony ring is 
completed by the attachment of the proximal end of the mb to both processes, 
recalling exactly the condition of the cervical vertebree of the Crocodiles. In several 
adult Hyperoodons’ skeletons, I have seen the upper and lower transverse processes of 
the seventh dorsal vertebra united so as to form a complete ring. 
It will be very important to ascertain whether Aogia and the Ziphioids agree in this 
respect with Physeter and Hyperoodon, as certainly might be predicated from their 
general affinities. With regard to the first-named, the only published description* of 
the skeleton at Sydney gives no information on this point; but the unique skeleton of 
the Micropteron sowerbyense, belonging to the last-named group, now in the Royal 
Museum at Brussels, shows the following characters:—The seventh dorsal vertebra has 
a transverse process springing from the arch; to this the tubercle of the seventh rib is 
articulated, while its head joins the body in the usual way. The eighth vertebra has 
no process from the arch, but one projecting from the body at a level with the facet 
for the attachment of the head of the seventh rib; to this the end of the eighth rib is 
fixed. The transposition of the transverse process from the arch to the body is thus 
as abrupt as in Physeter and Hyperoodon, the only difference being that the two pro- 
cesses do not coexist on any one vertebra as in those genera. ‘The principle, however, 
is the same. 
Lumbar Vertebra.—The eight lumbar vertebre present a remarkable similarity to 
one another, both in form and dimensions. ‘Their bodies increase slightly but pro- 
gressively in length from the first to the last. One of their most characteristic features 
is the form of their infero-lateral surfaces, much hollowed out and converging to a strong 
* Wall, op. cit. 
+ For the condition of the rib-attachments in Platanista and Inia, in some respects intermediate between 
those of the Physeteride and Delphinide, see “ Description of the Skeleton of Inia geoffrensis,” &c., Trans. 
Zool. Soc. vol. vi. pp. 98-103. 
