20 



Dinosauria Iguanodon. 



Hylseosau- 

 rus. 



Polacan- 



thus, 



Wall-case, 

 No. 4. 



I Hypsi- 

 lophodon. 



Table-case, 

 ; No. 16. 



! 



Small Glass- 

 case, y. 



Ig-uanodon 

 Mantelli. 

 Wall-case, 

 No. 6, and 

 Table-case, 

 No. 15. 



The long dermal spines of Hylceosaurus, another armed 

 Dinosaur from the Wealden, were arranged in a single row along 

 the central line of the back. 



The Polacanthus, or many-spined Dinosaur, from the Weal- 

 den formation near Brixton, Isle of Wight, appears, as regards 

 its dermal covering, to have been one of the most heavily 

 armed of these old dragons. Its body was protected by a series 

 of long, laterally-compresssd, and more or less acutely triangu- 

 lar osseous spines, and also by numerous plain and keeled 

 scutes ; whilst the pelvic region was covered by a large shield 

 or carapace of thick bone firmly united to the vertebrae and 

 ribs, like the carapace in a turtle. The tail was also protected 

 by strong bony dermal scutes. 



Many of the limb-bones and vertebrae of the back and tail 

 were found associated with the spines, but no remains of the 

 neck or head. 



The bases of the spines are broad and asymmetrical, show- 

 ing that they were arranged in one or more rows on either side 

 of the central line of the back. The largest of these spines 

 exhibited measures ten inches in breadth, and in height thirteen 

 inches. 



We are mainly indebted to the researches of Prof. Huxley 

 and Mr. J. W. Hulke for a knowledge of Hypsilophodon Foxi, 

 a small Dinosaur from the Wealden, about 4 feet in length. 

 The animal has four large and powerful digits to the hind 

 foot, and a small rudimentary fifth outer toe; an extremely 

 small fore foot (or manus), with four digits and a fifth rudi- 

 mentary one. The sharp-pointed and curved ungual phalanges 

 indicate that it was probably arboreal and rock-climbing in 

 its habits. The sides of the crowns of the teeth are finely- 

 serrated, and repeat in miniature the serrations of the crown 

 of the teeth of Iguanodon. Hypsilophodon was destitute of any 

 dermal armour. Remains of parts of several individuals have 

 been met with at Brixton, in the Isle of Wight. 



" Mantell's Iguanodon." This is one of the largest of the 

 great extinct land-reptiles, some of which certainly rivalled the 

 elephant in bulk. The femur (thigh bone) alone measured 4 

 to 5 feet in length. The fore-limbs were very short, so that it 

 is almost certain that it did not make use of them constantly 

 for progression on the ground, but could readily raise itself into 

 an upright position, the weight of its body being counter- 

 balanced by its long and ponderous tail, although it was far too 

 bulky to progress by leaping, after the manner of a kangaroo. 

 The slab in the centre of Case 6 contains a great portion of the 

 skeleton of a young individual of Iguanodon Mantelli from 

 Bensted's Kentish Rag quarry at Maidstone, in which the 

 disproportion of the fore and hind limb is well shown. It will 

 be seen that the bones of the arm and fore-arm (humerus, and 



