862 MB. F. G. PAESONS ON THE [Nov. 29, 



the tail these also gradually die away. There are altogether 

 31 free caudal vertebrae. 



The Sternum of Pedetes consists of the presternum, four meso- 

 sterual sternebrae, and the xiphisternum. The presternum is 

 considerably expanded anteriorly, but narrows suddenly behind the 

 attachment of the first rib. the 2nd, 3rd, 4th, and 5th costal 

 cartilages articulate opposite the joints between sternebra), the 6th 

 articulates with the posterior part of the last sternebra, the 7th 

 articulates with a cartilaginous mass separating the last sternebra 

 from the xiphisternum, while the 8th is attached to the anterior 

 part of the xiphisternmn. In the foetal specimen centres are 

 present for the presternum and first two sternebrae. 



The sternum of Dipus is very like that of Pedetes in the number 

 of elements present ; the chief points of difference are that the 

 8th rib does not reach it and that the first rib is attached nearer 

 the front of the presternum. 



The Clavicle both of Pedetes and Dipus is well marked and 

 has the initial / curvature as in man. In the foetal Pedetes the 

 shaft was entirely ossified, but the two extremities were carti- 

 laginous. 



The Scapula has much more the human shape in Pedetes than it 

 has in Dipus : this is due to the fact that the vertebral border 

 is much longer in comparison in the former animal than in the 

 latter ; there is a very faint indication of a metacromion process in 

 both animals. In the foetus the ala and spine alone were 

 ossified. 



The Humerus in Pedetes is half the length of the femur, there is 

 a fairly prominent pectoral ridge about the middle of the bone, 

 and the inner condyle is very prominent and curved upward into 

 a book-like process, but there is no bony supracondylar foramen. 

 The external supracondylar ridge is well marked. In the foetus 

 the shaft alone is ossified ; it is interesting to notice that in the 

 cartilaginous lower end of the bone there is a supracondylar 

 foramen. 



In Dipus the humerus is considerably less than half the length 

 of the femur ; in appearance it closely resembles that of Pedetes, 

 there is the same recurved internal condyle and prominent ex- 

 ternal supracondylar ridge, but the pectoral ridge is more strongly 

 marked. 



The Radius and Ulna in Pedetes are very strong and are shorter 

 in proportion than those of Dipus, which, besides being longer, are 

 much more dehcate : this contrast is doubtless due to the great 

 amount of digging which Pedetes has to perform. 



The Carpus of Pedetes consists of, in the proximal row, scapho- 

 lunar, cuneiform, and pisiform ; in the distal row, trapezium, trape- 

 zoid, OS magnum, and unciform. In the interval between the 

 scapho-lunar, trapezoid, and os magnum there is a small wedge- 

 shaped centrale, which is only visible on the dorsal side. Articu- 

 lating with the radial side of the scapho-lunar is the radial ossicle 

 or prsepollex : this structure agrees very closelj' with that figured 



