250 



Dr. Francis Baron Nopcsa — British Dinosaurs. 



region of Polacanthus measured 90-100 cm., and is thus considerably 

 shorter than the space which these spine-like ossifications cover. 

 Supposing, however, that the spines extended anteriorly right to 

 the back of the skull, as they do in HrjJccosaurus, and at least 

 7-8 cervical vertebrae to have been present, this agrees with the 

 length indicated by the double row of spines, and in consequence 

 one cannot help rebuilding Polacanthus in a ITylcBosatirtis-Yike manner. 

 The coexistence of large, asymmetrical, round, thick, feebly keeled 

 plates, together with the spines in question, shows furthermore that 

 the other, probably more inferior rows of the dermal covering were 

 not formed by spines, but b}' elements of another type ; these are 

 the single pieces that one cannot place in situ. 



Fig. 8. — Posterior view of a pair of anterior dorsal dermal spines of Polacanthus. 



Conclusion. 



The conclusions drawn from the fresh study of Polacanthus 

 are expressed in the reconstruction of the animal as carried out 

 by the ' mason formatori ' of the British Museum, Mr. Barlow, 

 under Dr. A, S. Woodward's and my superintendence ; and this 

 reconstruction afforded the basis for the Plate accompanying this 

 paper. Through this reconstruction Dr. Hulke's and the Eev. W. 

 Fox's general views about Polacanthus are nearly completely in 

 accord. Polacanthus was an animal of low stature, whose height 

 at the rump did not exceed three feet. Its strongly marked bones 

 and their large joints speak of its immense muscular power, whilst 

 the shortness of its limbs and the anchylosis of the lumbar vertebrae, 

 welding the loins and tlie sacrum into a long inflexible rod, give 

 probability to its having been a slowly moving vegetable-feeder. 

 With these characteristics one might venture to add the remark 

 that Polacanthus was a sort of Glyptodon among the Dinosaurs. 



EXPLANATION OF THE PAGE-PLATE XIL 



The shaded parts of the drawing indicate the parts actually preserved ; the rest has 

 been reconstructed according to tlie evidence afforded by Struthiomurus. 



