40 SCOTT. [Vol. V. 



very prominent and runs far down the shaft ; on the inner side 

 of its proximal end there is the usual deep tendinal sulcus. The 

 lower half of the shaft is flattened antero-posteriorly and is 

 transversely oval in section. The distal end is somewhat ex- 

 panded and thickened ; the external astragalar facet is some- 

 what larger than the internal, from which it is separated by a 

 tongue, much more prominent than in the existing types. In 

 each of these astragalar facets there is a shallow depression, 

 the beginning of the interruptions of the articular surfaces 

 which are so noticeable in the camel. The internal malleolus 

 is very prominent and is anterior in position. The fibular facet 

 is continuous from before backward, and though emarginated 

 by the groove for the rudimentary shaft of the fibula, this 

 groove is not nearly so deep as in the camel, where it divides 

 the facet into anterior and posterior portions. 



The fibula (PI. Ill, Fig. 41) is quite as much reduced as in 

 the modern representatives of the Camelida. The proximal end 

 is a small spine anchylosed with the tibia, and the distal por- 

 tion is a nodule which is wedged in between the tibia and the cal- 

 caneum, forming a heavy external malleolus. It projects further 

 beyond the line of the tibia than in the recent genera, and is 

 deeply grooved on its outer side by the sulcus for the peroneal 

 tendons. The nodule presents articular facets upon three of its 

 sides, a proximal one for the tibia which is not interrupted in 

 the middle, a distal one for the calcaneum, and an internal one 

 for the astragalus. 



The tarsus (PI. Ill, Figs. 43-47) is essentially like that of 

 the llama, but in correspondence with the lighter construction 

 of the limbs, is higher and narrower. The astragalus has a 

 narrower groove for the tongue of the tibia, and, indeed, is nar- 

 rower throughout. The external condyle is separated quite 

 widely from the distal trochlea, while the internal one is sepa- 

 rated from the navicular facet only by a small prominence. The 

 surface for the cuboid is quite narrow, that for the navicular 

 much wider and hour-glass-shaped. The calcaneum is relatively 

 longer and more slender than in the llama, and is especially 

 of less antero-posterior depth towards its distal portion, nor is 

 there any groove above the sustentaculum, to receive a process 

 from the tibia. When the calcaneum of the llama is viewed from 

 behind, there is seen a projection from the posterior part of the 



