LIASSIC FORMATIONS. 
53 
in the slab^ PI. XVIII, at 6fi, which crosses the right antibrachium ( 54 , 55). The deflected 
posterior ends of the condyles are here shown, and beneath them three tarsal bones 
( 0 , I, h), with the characteristic short and thick metatarsal of the fifth toe («?, 
The tarsal bone between the tibia! trochlea and the three metatarsals («, ii, in), 
answers to the astragalus, marked a, in Scelidosaurus and Crocodiliis (Monograph and 
Plate above cited) ; two tarsals, of which the one representing the second row is the 
smallest, intervene between the tibia and the fifth metatarsal ; the larger of these ossicles 
answers to the calcaneum (/ in Scelidosaurus and Crocodiliis, Monograph, ut supra), the 
smaller and distal one to the cuboides {Jj, ^A). 
The bony frame-work of the left foot (eg') is instructively preserved ; the first four 
metatarsals are, as usual, long and slender, and resemble those in previously described 
Pterosauria ; their under or plantar surface is exposed. The metatarsal of the first or 
innermost toe (^) is the shortest, that of the fourth toe {iv) is next in length ; the third {Hi) 
is the longest, but there is little difference in this respect ; their distal condyles project 
toward the sole, and are made trochlear by a mid-groove. 
The innermost digit shows the proximal and ungual phalanges in natural connection 
with each other and with the metatarsal : the ungual phalanx (^) is scarcely half the size 
of that of the corresponding digit (/) of the fore-foot. The ungual phalanges of the three 
other toes {ii, Hi, iv) are preserved, showing the usual uniformity of size in the hind- 
foot of Pterosauria : the number and disposition of the contiguous but scattered phalanges 
best accord with the phalangeal formula ( 3 , 4, 5) presented by the second, third, and fourth 
toes respectively, in better preserved feet of other Pterosauria (PI. XIX, fig. 5). There 
is, however, here unequivocal evidence of a fifth toe, and that not merely rudiruental but 
recognisably functional though without a claw. The tarsal bones (6, h) support a meta- 
tarsal {in, v) directed parallel with the metatarsals {i — iv), but much shorter and also thicker : 
it is 6 lines in length, and expanded at both ends, the proximal one being 2|- lines in 
breadth, the distal one 2 lines, and the middle of the shaft I^ line. The under or 
plantar side of the bone is exposed, as in the others, and shows a shallow oblique channel 
passing from the proximal end obliquely to the inner side of the shaft, dividing two 
elevations at that aspect of the proximal end. The distal end is a moderately convex 
condyle, the outer and plantar prominence of which is broken off. I regard this bone as 
the fifth metatarsal. It supports a digit of tw'o phalanges : the first (I, u) is slightly 
dislocated, so as to show the concavity of its proximal joint close to the condyle to which 
it was articulated : it is I inch 3 lines in length, and is thicker as well as much longer 
than the corresponding phalanx of the other toes. The second phalanx (2, v) is I inch in 
length : it is bent back upon the first, and gradually tapers to a point. Both phalanges, 
1 This throws expository light on the idea, revived by Gegenbaur (‘ Vergleichend-anatomische Bemer- 
kungen iiber das Fussskelet der Vogel,’ in Reichert’s ‘ Archiv fiir Anatomic, Physiologic, und wissensch. 
Medicin,’ 1863, p. 445), viz., that the distal trochlear epiphysis of the Bird’s tibia represents its proximal 
tarsal series, or astragalus. 
