Meukiam.] 



Triassic Ichth yopterygia . 



83 



sixty per cent, as long as the tibial, and is inclined about thirty 

 to forty degrees away from the plane of the latter. 



The larger of the elements next the distal end of the femur 

 has been considered as probably the tibia. Its length is almost 

 the same as its greatest width. The anterior border shows a 

 shallow median notch. The posterior margin has suffered con- 

 siderably from weathering, and it is not possible to determine its 

 outline with absolute deflniteness. As it now appears, this side 

 is concave, and, judging from the structure of the bone, it was 

 so originally. 



■ The fibula is better preserved than the tibia, and little doubt 

 can exist as to its original form. The distal end is considerably 

 wider than the proximal. The well-preserved posterior margin 

 is deeply concave. The anterior side has suffered considerably, 

 but appears to have had much the same form as the posterior 

 edge. Its length is the same as that of the tibia, but it is a 

 much slenderer bone. Its width at the proximal end is less than 

 two-thirds that of the tibia, the shaft is also much narrower. 

 The distal end is almost as wide as the corresponding part of the 

 tibia in its present weathered condition. Although the distal 

 extremities of the tibia and fibula may have been in contact, 

 there can be little doubt concerning the existence of a gap between 

 their middle or shaft portions. 



A portion of a small ossicle which originally lay between the 

 distal ends of the tibia and fibula may have been the intermedium, 

 or was possibly some other carpal or a phalanx. Another, which 

 is between the anterior proximal corner of the tibia and the 

 femur, is probably a loose phalanx, belonging with two seen a 

 short distance in front. This element might possibly be consid- 

 ered as a pre-tibial ossicle, but the space into which it seems to 

 fit would be largely closed up if the tibia were in its normal 

 position. As the tibia now lies, it is moved a little to the rear. 

 It would also be possible to make this a post-fibular ossicle like 

 that seen in some Plesiosauria and Ichthyosauria, if this were 

 considered the posterior side of the limb. It should, perhaps, be 

 stated that if both the limbs and the arches were considered as 

 reversed, or facing backward in the slab, they would come near 

 to agreement with the general plan of Pleisosaurian posterior 

 limbs and arches. 



