; ULKE—-KIMMERIDGE PLESIOSAURIAN REMAINS. 2 
1870 HULKE—KIMMEL URIAN REMAINS 621 
digits. As often as I looked at the cast of this gigantic paddle 
(63 feet long), I was struck with the insufficient basal support of the 
hindmost digit, and the suspicion forced itself upon me that some- 
thing was wanting in the postaxial side of the foot. |The Portland 
paddle proved this to be the case. Its second segment contains 
two coequal bones, and part of the distinct impression of a third, 
which has fallen out of the matrix ; and corresponding to this im- 
pression in the stone there is, as may be plainly seen in the excellent 
figure illustrating Prof. Owen’s memoir, the beginning of a second 
postaxial facet on the distal end of the femur. The rest of this 
facet, with the adjacent postaxial border, has been worn away. 
Prof. Owen regards the third ossicle in the cnemial row as “the 
homologue of the fabella which is present in some Plesiosauri (P. 
rugosus, for example), where its homotype in the fore limb is repre- 
sented by a detached olecranal process of the ulna,” adding “ that 
the bone in Pliosawrus portlandicus is relatively larger and less 
triangular in shape than in Plestosawrus rugosus.” Afterwards, 
describing the hindmost of the three bones present in the first row 
of the tarsus, which he regards as the calcaneum, Prof. Owen 
writes of its posterior border, “It appears to have been closely 
connected with the fabella (67'), which fits into the interspace 
between the fibula and the caleaneum; and whether to regard the 
ossicle marked 67' as the apophysial lever of the fibula or as the 
calcaneum may be a question ”*. 
The identity of the third cnemial bone of our Kimmeridge Plesio- 
saur with that which has left its impression in the matrix in which 
hes the Portland Pliosaurus-paddle cannot, I think, be questioned ; 
and the correspondence of this to the ossicle attached to the posterior 
border of the fibula of Plesiosaurus rugosus, pointed out by Prof. Owen, 
appears highly probable. If this be a true correspondence, and not 
simply an apparent one, the determination of the serial homology of 
the bone is still open; for no confirmation of either of the two hypo- 
theses is to be drawn from the Kimmeridge paddle. If the ossicle 
attached to the fibula in Plestosawrus rugosus is the homologue of the 
‘“‘apophysial lever of the fibula” (the styloid process of human 
anatomists), we have the anomaly of its lateral, not terminal, arti- 
culation with the shaft of the fibula, and also of its articulation with 
both the femur and the tarsus. If, however, it is the caleaneum, 
we have another anomaly—the articulation of the heel-bone and 
femur—besides the difficulty of reconciling this determination with 
that of the hindmost of the three bones of the first tarsal row, 
which the author of the memoir quoted regards also as the cal- 
caneum. 
We have not yet, I think, sufficiently complete material for the 
solution of this problem, and we must be content to wait for fresh 
material before the homology of the bone can be settled. At present, 
I will merely say that its existence as a coequal bone with the fibula 
and tibia in the Kimmeridge Plesiosawrus is in harmony with the 
ingenious theory of the type of limb-construction recently advanced 
* Paleont. Soc. vol. xxii. ‘ Fossil Reptilia of the Portland Stone,’ p. 11. 
