LOWER LIAS. 19 



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 

 artic ulation 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., w), 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 ( v ). The fourth metatarsal 

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

 1 inch 5 lines. The tibial angle of the proximal surface is most produced. The 

 fore-and-aft dimensions of the shaft do not exceed 6 lines. The second phalanx 

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

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

 length, 1 inch 2 lines in breadth. The ungual phalanx is 1 inch 6 lines in length; 

 8 lines across its articular surface, 1 1 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 

 surface correspond 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 effected in its remote successor of 

 the Wealden period, — the Iguanodon, by the suppression of the first, and by a 

 similar atrophy of the fifth digit. The foot-prints of Scelidosaurus would termi- 

 nate forward by the marks of four claws, the innermost falling short of the base 

 of the second, this and the fourth reaching the same line, and the intermediate 

 third claw extending farthest. The hind foot-prints of Iguanodon would be 

 tridactyle. 



The total length of the foot of Scelidosaurus is 1 foot 1 inch 6 lines ; the 



