530 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [June 25> 



from it a fourth and smaller metatarsal. I have extricated them 

 from the matrix, and placed them at the inner side of the pes, as the 

 form of the metararsal plainly indicates it to have had this position. 

 The three toes following this inner one, counted from the tibial to 

 the fibular border of the foot, have respectively 3, 4, 5 phalanges. 

 They answer therefore to the 2nd, 3rd, and 4th toes in the foot of 

 existing lizards ; and I assume the small displaced toe to be the 

 5th; in which case it wants the basal phalanx. The other basais 

 and the intermediate phalanges are stout, moderately long, and their 

 distal, pulley-shaped, articular surfaces are strongly marked. The 

 unguals are large, long, straight, and sharply pointed. They have 

 a very conspicuous marginal claw-groove. The third is the stoutest 

 toe ; and although it has one phalanx less, it is longer than the 4th, 

 the basal 2nd, 3rd, and 4th phalanges of which are shorter than any 

 others, in which respect they somewhat resemble those of the cor- 

 responding toe of the Iguanodon, 



Comparing Hypsilophodon with what is known of Iguanodon (for 

 its anatomy has still many voids), the following seem to me to be 

 some of the most striking resemblances and differences. Hypsilo- 

 phodon resembles the larger Dinosaur in the peculiar form of the 

 anterior extremity of its mandible, in the general facies of its com- 

 pressed sculptured teeth (longitudinally ridged and marginally ser- 

 rato-lamellated), in the form of the bones of the shoulder-girdle and 

 also in that of the haunch-bone, in the greater size of the hind 

 linib, the greater length and stoutness of the third toe (which cor- 

 responds in the number of the phalanges to the middle toe of Igua- 

 nodon). It differs from Iguanodon in having four toes *, in the 

 absence of that extreme shortness which marks the phalanges, espe- 

 cially of the outer toe of Iguanodon, and in the form of the unguals, 

 which are long, tapering, and pointed — in the tibia being longer 

 than the femur, the reverse of which obtains in Iguanodon — in the 

 inner femoral trochanter being nearer the proximal end of the 

 thigh-bone, and in the want of overhang of the margins of the an- 

 terior intercondyloid groove which marks the thigh-bone of Iguanodon 

 and of Hadrosaurus — and particularly, as regards the manus, in the 

 straight, symmetrical, distinctly claw-grooved unguals, which are 

 wholly unlike the shapeless depressed unguals of Iguanodon, devoid 

 of distinct groove for attachment of claw. 



Hypsilophodon resembles SeeHdosaumis Harrisonii in the number 

 of the pedal digits, and, superficially, in the facies of the compressed 

 teeth. This last resemblance, however, is weakened by a critical 

 examination of the specimens themselves. In both the crown is 

 separated from the root by a cingulum, the sides of which run out 

 on the lateral margins of the tooth ; but in Scelidosaurus no ridges 

 pass longitudinally from the cingulum to the trenchant edge of the 

 crown f, and the serration has quite a different shape. 



* Iguanodon has three functional toes only, the splint-like bone, thought to 

 represent a first toe, not being segmented into phalanges. 



t The artist has not been so successful as usual in the figure of a tooth which 

 illustrates Prof. Owen's memoir on the skull of Scelidosaurus in the Eoss. Eept. 



