1870. ] HULKE—KIMMERIDGE PLESIOSAURIAN REMAINS. 619 
sired. From the figure of the conjoined axis and atlas of the 
Haddenham specimen, given by the late Mr. L. Barrett in ‘ Annals 
& Mag. of Nat. Hist.’ 1858, and from some sketches of the coracoids, 
and of a restored paddle of the Ely one, there are evidently strong 
resemblances; but Mr. Davies, sen., of the Paleontological Depart- 
ment of the British Museum, whose opinion in a matter of this 
kind is justly entitled to great weight, tells me that he has seen the 
Haddenham spinal column, and believes it to represent a distinct 
species from Mr. Mansel’s. 
A comparison of the imbs of Mr. Mansel’s, and also of P. mega- 
dewrus, with those of the typical Liassic Plestosauri, brings out so 
many and such important differences that these two Kimmeridge 
Enaliosaurians may well rank as the representatives of a very distinct 
subgenus. 
Their coracoids are not produced forward mesially far in advance 
of the level of the glenoid cavity as they are in the Liassice Plesio- 
sauri, but their anterior borders make a nearly straight line. 
They are also much extended transversely to the trunk’s axis, while 
their greatest extension in the Liassic Plestosaur? is in the direction 
of the axis.. In this the coracoids of the Kimmeridge Plesiosauri 
show a resemblance to Ichthyosaurus; but their front border wants 
the characteristic Ichthyosaurian notch. 
The humerus and femur of Mr. Mansel’s Plesiosawrus are abso- 
lutely, as they are also relatively to the length of the spinal 
column, longer than in any known Liassic Plestosaurus. They are 
also more massive, and their muscular impressions are much stronger. 
Their subglobular articular caput appears to me to make a larger 
angle with the axis of the bone; and there is also the well-developed 
trochanter. The postaxial border has a larger backward curve; 
and the wing is much larger. The distal end of the femur (that of 
the humerus is incomplete ; but by analogy it should resemble that 
of the femur) has a third articular facet, while that of the humerus 
and femur of Liassic Plesiosaurt has two articular facets only. 
The second segment of the limb, the cnemion, contains three coequal 
bones, articulating with the three femoral facets, and answering to 
the tibia, fibula, and an additional element. The Liassic Plesiosaurian 
femur has only two distal facets, and but two principal bones in the 
second segment of the paddle. In some species, however (P. rugosus), 
a rudimentary third ossicle is present at the postaxial border of 
the fibula. The two principal bones, the tibia and fibula, in these 
latter Plesiosaurs are elongated in the direction of the axis of the 
limb, and they are very different in form from the tarsal bones ; 
whereas in the Kimmeridge Plesiosaurus the three coequal bones in 
the cnemion are lengthened transversely to the axis of the limb, 
and differ little in shape from the tarsals. In this formal indiffe- 
rentism of its cnemion and tarsus, Mr. Mansel’s Plesiosaurus has a 
resemblance to IJchthyosaurus; but the similarity is more than 
balanced by the third bone in its cnemion and the perfect formal 
difference of the digits. 
It is, however, in the subgenus Pliosaurus that the limbs most 
