a Pachypodfrom th^ Canih'idge Upper Ore&nsand. 309 



rudimental digit were fully grown, it would probably show 

 the features " Avhich characterize the claw-j)halanx which has 

 been mistaken for the horn of Iguanodon.'''' That horn has 

 been harped upon so steadily, that I will venture to wind it 

 once more. First, then, it is manifest that the determination 

 quoted is as pure a dream as a midsummer night could invent. 

 But in 1854 (Wealden Dinosauria, part 2) the illustrious au- 

 thor devoted many pages to a consideration upon this horn ; 

 and there, too, the bone which Dr. Mantell so confidently ex- 

 alted is degraded to being the support for an Iguanodon's toe- 

 nail, seemingly because Dr. Mantell had named it a horn. I do 

 not wish to defend Dr. Mantell, though I think that his scien- 

 tific instinct led to a conclusion which was philosophically 

 good ; nor do I wish to underrate the spirit of Prof. Owen's 

 protest that Iguanodon can by no means be inferred to have 

 had a horn because such a structm-e is found in Iguana. 

 Even if wrong in this particular case, it was important for the 

 progress of science that uniformitarianism should not creep 

 unopposed into comparative anatomy. But in the elucidation 

 of the truth it is desirable not to neglect facts ; and from the 

 time when Prof. Owen observed that '' the mutilated basal 

 , surface in no wise militates against the supposition of the co- 

 nical bone having been the terminal, unsymmetrical ungual 

 phalanx," &c. &c., to this day no foot has been found con- 

 taining a bone which resembles it; no indubitable terminal 

 phalange resembles it closely ; while it is closely matched by 

 Dinosaurian dermal armour, especially that of Scelidosaui-us. 

 That it was a nasal horn is highly improbable ; but that it is 

 a dermal spine of some Dinosaur seems almost certain after a 

 comparison of the specimens. And if any one, thirty years 

 ago, had had the opportunities which students have, now in 

 the national collection, I venture to think that Dr. Mantell's 

 horn would never have been made to claw the dust. ; 



The bones of the metapodiuni of AcanthophoUs^ placed toge- 

 ther, measure over their proximal ends 9 inches from side to 

 side, while the middle bone is about 6 inches long ; they are 

 well expanded at the proximal and distal ends ; and the shaft 

 becomes more slender from the first to the fourth. The 

 proximal ends of all are flattened, transversely truncated, and 

 slightly twisted outward 5 while the distal ends are rounded 

 from above downward, and approximate to the usual pulley- 

 shaped articulation. The bones are all slightly worn, and 

 have suffered a little abrasion at their articular surfaces. 



The first bone is short and strong. The fiat proximal arti- 

 culation is shaped in outline like half of a wide pear, with the 

 convex surface external, the vertical cut surface internal, and 



