1056 
MR. J. W. HULKE ON THE OSTEOLOGY 
which merges into a relatively slender shaft, widening and flattening distally towards 
the carpal extremity; the breadth of which appears to be somewhat less than that 
of the corresponding part of the ulna. 
In the carpus (Plate 79, fig. 3) (through which unfortunately passes a crack filled 
with carbonaceous matter) a proximal row of ossa Carpalia is clearly recognisable. 
This appears to me to comprise a wedge-shaped os ulnare proximally articulating with 
the ulna and radially with a polygonal os intermedium, whilst its distal border 
corresponds to the base of the IVth., and slightly to that of the Illrd. metacarpal 
bone. The intermedium is proximally in relation chiefly with the ulna, but its radial 
border touches the lower end of the radius here coming into contact with an ossicle, 
which from its situation with respect to the radius must be regarded as an os radiale. 
This is unfortunately damaged by the crack through the rock already mentioned. 
Distally the os intermedium corresponds principally to the base of the Illrd., and in a 
less extent to that of the Ilnd. metacarpal bone. The os radiale is opposed distally 
to the base of the 1st. and slightly to that of the Ilnd. metacarpal bone. The 
condition of this part of the fossil does not permit me to speak confidently of the 
presence of a distal row of Carpalia. 
Five digits are recognisable : numbering these from the radial to the ulnar border of 
the paw, the 1st. metacarpal is 17 centim. long, and so is slightly shorter than the Ilnd., 
which is 1'85 centim. long. This, again, is slightly exceeded by the Illrd., which is 
1*95 centim. or 2 centims. long, and is the longest one, the IVth. attaining only 
1*2 centim.; whilst the length of the bone which I regarded as the Vth. metacarpal is 
only 8 millims. In its shape and its proportions this bone has more resemblance to 
a digital phalanx than the other metacarpals, but in these very points, as also in its 
different direction to that of the other metacarpals, it corresponds so well to the Vth. 
metacarpal in Iguanodon Mantelli that I may not hesitate to regard it as such. 
Proximally it articulates with the os ulnare. Its distal end is pulley shaped, distinctly 
articular. The phalangeal continuations of the toe are missing. On a small scale the 
shape and proportions of the other metacarpals repeat the metatarsals and do not 
require particular description. 
In the 1st. toe two digits are discernible. In the Ilnd. toe three phalanges are appa¬ 
rent, of which the proximal is nearly hidden by that of the Illrd. toe. This latter 
(the Illrd.), the line of which is slightly displaced from that of its metacarpal, certainly 
has four phalanges, the lengths of which are 9 millims., 5'5 millims., 4 millims., and 
8 millims. (the lengths of the proximal and 2nd phalanges of the Illrd. hind toe of the 
same skeleton are 2'5 centims. and 2*1 centims.). 
It is fortunate that the number of phalanges, four, in this toe (Illrd. of manus) is 
beyond question, because this shows an essential structural difference between the fore 
foot of Hypsilophodon and that of Iguanodon Mantelli, in which, upon the evidence of 
undisturbed specimens in the Brussels Museum, no digit has more than three phalanges. 
In the IVth. toe of our fossil the proximal phalanx is succeeded by a second, of which 
