1873.] HTJLKB ANATOMY OF HTPSILOPHODON FOXII. 523 



centrum in the same block of stone with the skull further enabled 

 Mr. Huxley to identify Hypsilophodon with the Mantell-Bowerbank 

 skeleton. 



In the discussion which followed the reading of this paper I 

 alluded to part of a reptilian skeleton from the same cleavage-bed, 

 shown me by Mr. Fox in 1869, which I considered to belong to 

 Hypsilojphodon. It consisted of a connected chain of several pre- 

 and postsacral vertebra, the right ilium with the proximal end of 

 the femur in the acetabulum, and the distal half of the leg with the 

 tarso-metatarsus. The ilium was prolonged forward for a con- 

 siderable distance in front of the acetabulum. The knee-joint had 

 been worn away ; but its position in the block, ascertained by pro- 

 longing the directions of the remaining parts of the tibia and femur, 

 made it very probable that the leg was longer than the thigh. 



The above are all the published notices of the anatomy of Hypsi- 

 lophodon Foxii with which I am acquainted. 



In several visits to the Isle of Wight I have obtained additional 

 evidence of its structure ; and having quite recently been so fortunate 

 as to exhume from the same Cowleaze bed great part of a skeleton 

 of this reptile, I am now able to communicate many details respect- 

 ing its dentition, and also the form of the mandibular symphysis, 

 not illustrated by Mr. Fox's skull, as well as the forms and propor- 

 tions of several bones of the shoulder and hip-girdles, and fore and 

 hind limbs, before unknown. 



Probably the entire skeleton was present ; but its immaturity and 

 the fissured state of the clay in which it was lying were so un- 

 favourable to the preservation of the bones, that most of them were 

 too much shattered to bear removal, and of many I could only bring 

 away ideas, the bones themselves falling into numberless small 

 pieces, which no pains or ingenuity could join. 



Skull. — The only remnants of this which I could save were parts 

 of the jaws and of one orbit. In the clay filling the orbit were 

 several small osseous scales, which I judged to be vestiges of a 

 sclerotic ring ; and deeper than these was a large and extremely thin 

 bony lamina, apparently an extensively, if not, indeed, completely, 

 ossified interorbital septum. 



The largest piece of jaw is the right mandibular ramus (PL XVIII. 

 fig. 1). The outer surface and dentary border are laid bare. Its 

 length from the front of the symphysis to the front of the quadratic 

 joint (behind which the bone is defective) is 2-5 inches. The upper 

 border slants from the quadratic joint steeply upwards to the coronoid 

 process, the top of which is wanting ; and from here it declines gently 

 forwards through a space of 1*6 inch, which comprises the entire 

 tooth-bearing portion. In front of this, at the distance of '35 inch 

 from the symphysis, it abruptly falls ; and the surfaces, which behind 

 this point look inwards and outwards, acquiring an upward and 

 downward aspect, one half of an edentulous mental interdentary 

 groove (fig. 1, a) repeats in miniature the characteristic depressed 

 symphysis of fguanodon. In front of this extremity of the mandible, 

 and quite distinct from it, is a thin triangular plate, which I suspect 



