612 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 22, 
give the centra some resemblance to those of Ichthyosaurian ver- 
tebre, from which, however, they may be at once distinguished by 
the absence of costal tubercles from the outer surface, and by the 
circumferential swelling of the articular face. But these vertebre 
are sharply differentiated from those of Jchthyosaurus by their 
anchylosed neurapophyses bearing long transverse processes. These 
are laterally compressed blades directed upwards and outwards from 
the neural arch. Their outer end is slightly swollen, and cut 
obliquely, which makes the upper border of the process longer than 
the lower one, and gives the terminal rib-bearing surface an almost 
directly outward aspect. 
The anterior articular processes spring from the crown of the arch, 
immediately above the neural canal. Their lower ends meet, and 
their upper ones are incurved, so that together the two prezygapo- 
physes form about two-thirds of a circle, each half of which looks 
inwards and embraces the corresponding posterior articular process, 
the shape of which, and the aspect of its articulating surface, are 
the counterparts of those of the anterior one. The posterior arti- 
cular processes spring from the back of the arch just below the 
root of the neural spine, in a rather higher level than that of the 
anterior. The neural spines are long and straight. 
The ribs have a simple flattened head, separated by a slight con- 
striction from the angle 34 inches distant, beyond which they sweep 
outwards and downwards in an even curve. Their upper, convex 
border is thick, the lower one is thin, and a shallow groove parallel 
to the upper one channels the surface of the rib. 
The digital phalanx had the usual cylindrical figure, with con- 
stricted middle of a Plesiosaurian digit-bone. It is 1-5 long, -9 
broad at ends, -5 broad at middle. 
Przsrosavrus Mansexit (Pl. XLI. figs. 1-6). 
In November 1868 Mr. Mansel kindly sent me for examination 
a large series of vertebra, evidently comprising the greater part of 
the spinal column of a Plesiosawrus, with pieces of the two humeri, 
and several incomplete flat bones, which some years before had been 
discovered in the cliffs east of Clavell’s Tower, in Kimmeridge Bay. 
Mr. Mansel informed me that he had himself supervised their ex- 
humation, and that the bones were associated in such a manner as to 
leave no doubt in his mind that they had all belonged to one indi- 
vidual ; and he also mentioned that, under the impression that they 
were Pliosaurian remains, he had enclosed the four great paddle-bones 
with carpals and many phalanges in a case of Pliosaurian fossils 
which he had presented to the British Museum. It was Mr. Man- 
sel’s first impression that all the four limb-bones had been enclosed 
in this case; but the parts actually sent were the nearly complete 
left femur, the proximal half of the right one, and the distal half of 
the left humerus. On recently taking to the Museum the proximal 
halves of the humeri which Mr. Mansel sent me in November 1868 
(with the spinal column) one was found to fit exactly the distal 
fragment of the humerus already in the Museum; and the national 
collection now contains the nearly perfect femur and left humerus 
