LIASSIC FORMATIONS. 



53 



in the slab, PI. XVIII, at 6(], wliicli crosses the right antibrachiiiin (ji, :>;")). The deflected 

 posterior ends of the condyles are here shown, and beneath them three tarsal bones 

 {o, 1, b), with the characteristic short and thick metatarsal of the fifth toe {m, v)} 



The tarsal bone between the tibial trochlea and the three metatarsals [i, ii, Hi), 

 answers to the astragalus, marked a, in Scclidomurus and Crocodilns (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 Scelidosniirus and Crocodilus, Monograph, ut supra), the 

 smaller and distal one to the cuboides {b, ib.). 



The bony frame-work of the left foot (69') is instructively preserved ; the first four 

 metatarsals are, as usual, long and slender, and resemble those in previously described 

 Ptcrosauria ; 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 {in) 

 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 Pferosauria : the number and disposition of the contiguous but scattered phalanges 

 l)est accord with the phalangeal formula (3,4, 5) presented by the second, third, and fourth 

 toes respectively, in better preserved feet of other Pferosauria (PI. XIX, fig. 5). There 

 is, however, here unequivocal evidence of a fifth toe, and that not merely riidiinental but 

 recognisably functional though without a claw. The tarsal bones {b, b) support a meta- 

 tarsal {7)1, v) directed parallel with the metatarsals {i — iv), but much shorter and also thicker : 

 it is lines in length, and expanded at both ends, the proximal one beuig 2^ lines in 

 breadth, the distal one 2 lines, and the middle of the shaft H 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. Tlie 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 two phalanges : the first {\,v) is slightly 

 dislocated, so as to show the concavity of its proximal joint close to the condyle to which 

 it was articulated : it is 1 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 1 inch in 

 length: it is bent back upon the first, and gradually tapers to a point. Both j)halanges, 



^ This throws expository light on the idea, revived by Gegenbaur (' Vergleicheud-nnatoniische Bemer- 

 kungcn iiber das Fussskelet der Vogel,' in Reichert's ' Archiv fiir Anatomie, Physiologie, und wissenscli. 

 Medicin,' 18G3, p. 44.")), viz., that tlie distal trochlear epiphysis of the Bird's tibia represents ils proximal 

 tarsal series, or astragalus. 



