LIASSIC DINOSAURS. 117 



1 incli 8 lines ; the fore-and-aft breadth is 2 inches 1 line. The thickness in this 

 direction diminishes rapidly towards the distal end ; the transverse dimension 

 decreases in a much less degree ; this, at the middle of the bone, being 1 inch 2 

 lines, whence it increases to a distal transverse breadth of 1 inch 11 lines. The 

 configm-ation of this articular surface resembles that of the second metatarsal ; the 

 fore-and-aft breadth of the condyle is 1 inch 6 lines. The proximal phalanx of 

 the third toe (ib.,m, l) is 1 inch 2 lines in length, 1 inch 10 lines across the base, 

 and 1 inch 3 lines across from before backwards. On the middle of the outer 

 border is a tuberosity ; each side of the distal end is deeply impressed ; the distal 

 articulation resembles that in the second toe. The greatest transverse breadth of 

 this phalanx is 1 inch 7 lines. The second phalanx (ib., 2), with a basal breadth 

 of 1 inch 6 lines, is only 1 inch 7 lines in length. The distal articulation is 1 inch 

 5 lines in breadth. The third phalanx (ib., .3), with a basal breadth of 1 inch 3 

 lines, is 1 inch 2 lines in length, with a distal breadth 1 inch 1 line. The ungual 

 phalanx (ib. 4) is more depressed in proportion to its breadth than that of the 

 preceding toe ; in other respects it resembles it in shape. 



The fourth metatarsal (ib., iv), is 4 inches 5 lines in length, of an unsymmetrical 

 figure, receding from the middle metatarsal along its distal half, which is concave 

 lengthwise on the tibial side ; the fibular side presents a general but slighter con- 

 cavity; this metatarsal is triedral, the fore and back surfaces converging to an 

 obtuse, narrow, outer border, significant of its terminating that side of the foot 

 beyond the representative style of the fifth digit (y). The fourth metatarsal mea- 

 sures 1 inch 9 lines across the base and 1 inch 7 lines from before backwards, at 

 the tibial side of the base ; the fibular side being reduced to the narrow rough 

 ridge for the ligamentous attachment of the fifth abortive metatarsal. The breadth 

 of the shaft of the fourth metatarsal at its lower third is 1 inch 1 line ; that of the 

 distal articular surface is 1 inch 5 lines. The first phalanx of the fourth toe is 

 1 inch 11 lines in length ; the basal breadth is 1 inch 8 lines and the distal breadth 

 is 1 inch 6 lines. The tibial angle of the proximal surface is most produced. The 

 fore-and-aft dimensions of the shaft do not exceed G lines. The second phalanx is 

 1 inch 2 lines in length, and 1 inch 3 lines in basal breadth. The third phalanx is 

 ] inch in length, 1 iucli 4 lines in breadth ; the fourth phalanx is 9 lines in length, 

 1 inch 2 lines in breadth. The ungual phalanx is 1 inch G lines in length ; 8 Hues 

 across its articular surface, 11 lines across its broadest part, caused by the aliform 

 expansions of the bone beyond the articulation. It curves downwards and inwards, 

 or towards the tibial side, to a subacute apex ; the characters of its sui'face corre- 

 spond with those of the larger ungual phalanges of the preceding toes. 



From the abortion of the fifth digit, and the disproportionate shortness of the 

 first, we have in Scelidosaurus the example of a reptile manifesting a tendency to 

 the tridactyle type of the hind foot, and this is eflfected in its remote successor of 



