246 Dr. Francis Baron Nopcsa — British Dinosaurs. 



Femur. 



The femur of Polacanthis differs by its proximal and distal 

 expansion very markedly from the same bone in Dacenturiis, 

 Stegosaunis, or even, though less so, from Scelidosaurus, and can 

 only be compared with Strutliiosaurus from the Gosau formation. 

 Among mammalia it is not with the Proboscidea that the Polacanthus 

 femur should be compared, but rather with Dinoceras, and this is of 

 no small interest, since it is the Proboscidean femur that the femur 

 of the Stegosaurians and Sauropoda seems to have imitated. In 

 my forthcoming Dacenturus paper I intend to ventilate also this 

 question which, to a certain extent, has already been noticed by the 

 late Professor Hatcher. 



Dermal Armour. 

 As Hulke mentioned in 1881 and 1887, one can distinguish in the 

 dermal armour of Polacanthus flat plates which are united by 

 synostosis and form a buckler covering the sacrum and the lumbar 

 region ; besides, there are small button-like round scutes which, as 

 in Dylceosaurus, belong to the end of the tail ; then there are keeled 



Fig. 5. — Two of the posterior caudals of Polacanthus, side view. 



high roof-like scutes which also belong to the caudal region, fui'ther 

 on heavy spines rising from a flat triangular base, and besides 

 this large oval plates which show a rounded keel near the middle. 

 It can be seen that in this particular the dorsal ossifications of an 

 animal show a great amount of specialisation. 



The sacrolumbar buckler is well known, being figured and 

 described by Hulke in a supplementary note in 1887. It is to be 

 noticed that the anterior margin is thinned out, thus indicating that 

 the abrupt anterior end is not due to fracture. 



Some other points have, however, till now entirely escaped 

 attention. In Hulke's figure in 1887, plate 9, the last lumbar ribs 

 are drawn as if a thinning out towards the margin were to be expected. 

 This is, as an inspection showed, and as Seeley already pointed out in 

 bis sketch of the Polacanthus pelvis, not the case, but the ribs terminate 

 nearly at the median dorsal margin of the ilium, or are extended 

 somewhat beyond and above the prfeacetabular process of the ilium. 

 As Professor Seeley has already pointed out, the structure of the 

 ilium bears a remarkable resemblance to the same part in Omosaurus 

 and Stegosaurus, but I do not think it is dessication, as Seeley 

 modestly puts it, to which we owe since 1892 the visibility of the 



