3852 Rk. Lydekker—Oxford and Kimeridge Clay Sauropterygia. 
light is the structure of the pectoral girdle. It will be remembered 
that the genus Murenosaurus was founded upon a supposed peculiarity 
of this part of the skeleton—to wit, that the preaxial border of the 
coracoids was not connected by a median bony bar with the pre- 
coracoids (using the terms employed by Mr. J. W. Hulke). Now 
the new specimens show that this restoration of the pectoral girdle 
is solely due to the imperfection of the type specimen; and, as Mr. 
Leeds at once pointed out to me, the portion of the scapulo-precora- 
coid regarded as the precoracoid in the figure given in the Q J.G.8. 
vol. xxx. p. 448, and made to meet its fellow in the middle line, is 
really the dorsal part of the scapula. The pectoral girdle is in fact 
of the same general structure as that figured by Prof. Seeley on 
p. 447 of the same volume as the type of the so-called Colymbosaurus ; 
and there appears to be no distinction, so far as regards the pectoral 
girdle (on which the two were founded), of both Murenosaurus and 
Colymbosaurus from the earlier EHlasmosaurus of Prof. Cope. If, 
however, we follow Mr. Hulke in retaining the Jurassic and 
Cretaceous Sauropterygians exhibiting this modification of the 
pectoral girdle in the original genus. Plesiosaurus, of which they form 
a well-marked group, then we may continue to use the name 
Plesiosaurus plicatus for this species. An allied, and apparently 
unnamed species, represented in Mr. Leeds’ collection, and dis- 
tinguished by its shorter cervical vertebra, which are also fewer in 
number, is also known to me by a considerable portion of a skeleton 
obtained from the Oxford Clay of Weymouth. This form I shall 
describe, and if necessary name on a future occasion; Mr. Leeds 
having kindly lent me one.of the cervicals of his mature example. 
The next species I have to mention is P. Oxoniensis, represented by 
several nearly entire skeletons in the Eyebury Colléction. Of the 
specific identity of these examples I have satisfied myself by a com- 
parison with the type cervical and dorsal vertebra in the Oxford 
Museum. ‘This species was referred by Prof. Seeley to a subgenus 
of Murenosaurus—I presume on the evidence of a pectoral girdle 
figured in Phillips’s “Geology of Oxford” (p. 810), which is turned the 
wrong way upward and described as the pelvis. The coracoids 
(pubes) in that example are, however, I believe, referable to the 
so-called Plesiosaurus philarchus; and the Eyebury specimens show 
that the pectoral girdle was of the type of the so-called Colymbo- 
saurus. These specimens show, moreover, that the remarkable 
pectoral limb from the Oxford Clay of Bedford, figured by Phillips 
on p. 815 as a pelvic limb, and made the type of P. eurymerus, is 
really referable to P. Oxoniensis ; the limb figured on p. 312 of the 
“Geology of Oxford” under the latter name apparently belonging 
to P. plicatus. 
A fourth species represented in Mr. Leeds’ collection is the so- 
called Plesiosaurus philarchus of Prof. Seeley, characterized by its 
long mandibular symphysis. The examples of this species show 
that in the young there were two distinct costal facets in the cervical 
vertebre ; while the teeth, and pectoral and pelvic girdles, present 
a great resemblance to those of Pliosaurus. This species seems to 
