1865.] = MR. W. H. FLOWER ON PHYSALUS SIBBALDII. 473 
short but distinct inferior process, which in that at Utrecht is re- 
presented by a mere tubercle. In the terminal caudal vertebre 
there is a great similarity: the last is very small, short, and disk- 
like; the second from the end is of similar form, but somewhat 
larger ; the third presents a sudden increase of size in every direction, 
so marked that, if it did not occur in both skeletons, one might 
easily suppose that a bone had been lost from this region. 
3. Skull.—The principal peculiarity of the skull, which I pointed 
out in the Utrecht specimen, was the breadth of the rostral portion ; 
this is repeated, though to not quite the same extent, in the Hull 
skeleton. The breadth across the middle of the beak of the former 
is to the length of the skull as 27 to 100, in the latter as 26 to 100. 
In six specimens of P. antiquorum it varies between 18 and 21 to 
100. The actual breadth (measured across the upper surface fol- 
lowing the curve) in the Hull specimen is 33", each maxillary being 
10" and the premaxillary 5", the space between the latter 3, The 
nasal bones agree together, and differ from P. antiquorum in being 
but slightly hollowed on their upper surface and anterior margins. 
This character is most strongly marked in the Hull specimen. 
4. The stylo-hyals are thicker, especially near the lower,end, in 
both the Utrecht and Hull skeletons than in the common Fin- Whale. 
5. The sternum, which is so remarkable in the Utrecht specimen 
for its almost rudimentary state, is, unfortunately, wanting in the 
Hull skeleton; but even this absence may not be without signifi- 
cance, for if it had been a large, well-developed bone, it is most un- 
likely that it should have been lost in a skeleton prepared with such 
care as to be in every other respect perfect. 
6. Rzbs.—In the Utrecht skeleton (not articulated) I counted but 
fifteen pairs; while in that at Hull there are sixteen, the last well 
developed—as long, in fact, as those which precede it. If one could 
be certain that one pair had not been lost in the former case, this 
difference might be of some importance ; but in different specimens 
of P. antiquorum the last rib is in some completely developed, and 
in others represented by a mere splint of bone totally unconnected 
with the vertebral column, and therefore easily overlooked in pre- 
paring the skeleton. If sixteen is the normal number of the pairs 
of ribs in P. sibbaldii, this makes a good specific distinction from 
P. antiquorum, which has never been known to have more than 
fifteen. The first rib agrees in both specimens, and differs from P. 
antiquorum in wanting a well-developed capitular process. In the 
Utrecht specimen this process is present in the second, third, and 
fourth ribs—longest in the third. In the Hull skeleton it is found 
from the second to the sixth, being longest in the third and fourth. 
In P. antiquorum it is usually longest in the second, and obsolete 
in the fourth. 
7. The phalanges of the digits of both skeletons are articulated 
artificially, and yet they correspond exactly in number and arrange- 
ment, except that the Hull specimen has an additional bone on 
digit III. The numbers are—II. 4; III. 5 (Utrecht), 6 (Hull) ; 
IV. 5; V.3,—an arrangement differmg somewhat from that of P. 
Proc. Zoox. Soc.—1865, No. XXXI. 
