1864.] | IN THE MUSEUMS OF HOLLAND AND BELGIUM. 417 
Sibbaldius.—Of this genus there is a very interesting skeleton, 
almost the exact counterpart in size to that in the Leyden Museum. 
It was obtained by Eschricht from the North Cape. The condition 
of the epiphyses shows that it is young, they being all non-united both 
in the vertebral column and long bones ; but the ossification of the 
transverse processes of the cervical vertebrae has proceeded further 
than in that at Leyden. The skeleton is well articulated, and gives 
now a total length of 31' 8"; but about 6” must be added for the 
end of the tail, which is wanting. The dimensions of the skull are 
given in the Table at p. 402. The nasals are narrow, cut off nearly 
straight at their anterior ends, slightly hollowed on each side above. 
The lachrymals are thickened at their outer edge. The orbital pro- 
cesses of the frontals broad externally. Lower jaw light, little curved, 
and with a short triangular coronoid process. 
There are 7 cervical, 14 dorsal, and 32 lumbo-caudal vertebree 
present ; about 5 of the latter are absent, which would make a total 
of 58. The atlas has the usual characteristics of the genus. The 
transverse process of the axis forms a complete ring, the aperture of 
which has a length of 23" and height of 2". The whole process is 
53" long, but is incomplete at the end; it is 53! in height at the 
middle, and the opening is situated much nearer the upper than 
the lower margin of the process. In the third vertebra also the 
upper and lower processes are united ; in the fourth, fifth, and sixth 
they are separate. The lower one of the sixth is shortest, broad, and 
twisted on itself. In the seventh the inferior process is represented 
by a small tubercle. 
There are 13 ribs present on the right side, and 14 on the left. 
The fourteenth is very much thinner than the others, twisted backwards 
at its lower end, with a very slender head, articulated to the transverse 
process of the vertebra. ‘The first pair of ribs have double heads ; 
but the anterior head on both sides is very incompletely developed, 
and on the right side completely detached from the remainder of the 
bone ; it has a pointed end below, merely applied to the main part of 
the rib; so that if it had been lost in maceration, this rib might have 
been supposed to be simple. On the left side it is ankylosed, but 
very slender. It would be interesting to ascertain, by the examina- 
tion of younger specimens, whether this anterior head has always a 
separate centre of ossification, as it is not improbable that this sin- 
gular double-headed bone is in reality formed by the coalescence of 
two originally distinct ribs. The second, third, and fourth ribs have 
small capitular processes. The stylo-hyals are very flat, but not so 
broad proportionately as in the Java Whale, being 11" long and 33" 
in greatest width. The bones of the fore limbs present the same 
general characters and proportions as in the Leyden specimen from 
the Zuyder Zee. The sternum is absent. 
This specimen has been previously mentioned in this paper as an 
example of Siblaldius laticeps, Gray, presenting some interesting in- 
dividual deviations from that at Leyden, referable to the development 
of the two skeletons not having proceeded pari passu in all parts of 
the system. 
Proc. Zoou. Soc.—1864, No. XXVII. 
