234 J. W. HULKE ON POIKILOPLEURON BUCKLANDI. 
astragalus and other bones of fore and hind feet; and many ribs, 
forming a costal apparatus of singular complexity, which suggested 
the generic name Porkilopleuron. For a long time Deslongchamps 
thought these remains might belong to Megalosaurus; but after 
much consideration, the weight of evidence then available appeared 
to him adverse to this, and he therefore gaye his Saurian the 
distinctive generic name Potkiloplewron, attaching to it, as he 
distinctly tells us, the specific name Bucklandi, the same as the 
trivial name of Megalosaurus, in order that if future discoveries 
should identify it with this, the identification would involve only 
the suppression of a generic denomination. 
Deslongchamps regarded his Poikilopleuron as holding an inter- 
mediate position between Crocodiles and Lizards. Three years after 
the publication of this memoir Porkilopleuron was adopted by 
Prof. Owen, and placed by him in the order Crocodilia, between 
Steneosaurus and NStreptospondylus*; and very recently this 
eminent paleontologist has reaffirmed this position on the evidence 
of a chain of vertebra, considered by him to indicate a small 
species of Povkilopleuron, which he names P. pusillus, in the col- 
lection of the Rev. W. Fox. As this chain shows the sacrum 
of the animal to have consisted of two vertebree, the same as in 
Crocodiles, Prof. Owen considers that it proves the Poikilopleuron to 
have been a Crocodile, and not a Dinosaur as Dr. J. Leidy sug- 
gested, in 1873, in his description of the vertebrae assigned by him 
to a species of Potkiloplewron which he named P. valenst. In 
1869 it had, from the similarity of its astragalus to that of Mega- 
losaurus, been placed by Prof. Huxley in the family Megalosauride 
of the order Dinosauria. 
The necessary evidence for deciding the true position of Deslong- 
champs’s Potkilopleuron in the class Reptilia, and also for solving the 
question of its individual distinctness, is fortunately to be found in 
the numerous and excellent figures he has left us of its remains. 
These, fortunately, comprise very exact and carefully executed 
representations, from several points of view, of some of the test- 
bones of Dinosauria. I refer particularly to the tibia and astra- 
galus. Its tibia, represented in pl. vii. figs. 3, 4, is manifestly 
that of atypical Dinosaur ; the form of its distal end is too plain to 
admit of any doubt on this point. The subdivision of the articular 
surface of this end of the shin-bone into an imner and an outer 
moité, with their surfaces differently inclined and so adapted to 
the corresponding hollows in the upper surface of the astragalus as 
to be incompatible with motion between these bones§, the pro- 
jecting angle shown on its postero-internal surface, and the entering 
angle depicted in its antero-external surface, for lodging the ascend- 
ing process of the astragalus, are singly and collectively known 
* Brit. Foss. Rept. in Brit. Assoc. Rep. 1841, pp. 84-88. R. Owen. 
t ‘Foss, Rept. Wealden and Purbeck,’ Suppl. vii. p. 1, pl. 1 (1876), Pal. Soc. 
vol. R. Owen. 
{ Extinct Vertebrate Fauna, part 1, pp. 279 and 388. J. Leidy. 
§ Mém. cit. pl. vi. fig. 7. 
