R. Lydekker—Oxford and Kimeridge Clay Sauropterygia. 351 
collection as fully as I might desire. On arrival, my astonishment was 
unfeigned to find that this collection comprised not, as I expected, only 
one or two imperfect skeletons of one or more species, but in some 
cases as many as five or six almost entire skeletons belonging to as 
many individuals of four well-defined species. The specimens are 
arranged on shelves and in trays in two rather small rooms, which 
they almost completely fill; and so perfect are many of them that 
there would be no great difficulty in mounting entire skeletons of 
these extinct Saurians in the same manner as those of existing 
Cetaceans are exhibited in our Museums. In many cases every 
process and spine of the vertebrze is absolutely perfect, owing to the. 
careful and patient manner in which Mr. Leeds has personally 
extracted the skeletons from the soft clay in which they lay embedded. 
The paddles too, which have been such a stumbling-block to the 
paleontologist, have every bone in its natural position, so that there 
can no longer be any doubt as to their mode of arrangement. 
Apart, however, from the intrinsic perfection of this collection, 
its great importance consists in the clearing up of the relations and 
affinities of the many so-called species of Sauropterygians which 
have been described upon more or less imperfect remains from the 
Oxford Clay. In order to avail myself of the full advantages to be 
gathered from a visit to this collection, I had carefully studied all the 
specimens previously described from this horizon ; and, through the 
courtesy of Prof. A. H. Green, I had the further advantage of having 
the type vertebrae on which the late Professor Phillips founded his 
Plesiosaurus Oxoniensis and P. plicatus at the British Museum. 
Fic, 1.— Posterior (1), hemal (2), and anterior (3) aspects of a cervical vertebra of 
Plesiosaurus plicatus, from the Oxford Clay, 5. (After Phillips.) 
The first skeleton to which I directed my attention was the some- 
what imperfect one which Prof. H. G. Seeley described some years ago 
in vol. xxx. of the Geological Society’s Journal, under the new generic 
and specific name of Murenosaurus Leedsi. Since that specimen was 
found Mr. Leeds has obtained several other much less imperfect 
skeletons of both immature and adult individuals, which he refers, 
and in my judgment quite correctly, to the same species. The 
immature skeletons show, however, that the cervical vertebra are 
quite indistinguishable from those from the Oxford Clay near Oxford, 
to which Prof. Phillips applied the name P. plicatus (Fig. 1) ; and the 
specificname Leedsi must, therefore, yield place to this earlier one. The 
most important point, however, on which these new skeletons throw 
