874 MR. r. G. PARSONS ON THE [NoV. 29, 



to the Dipodidse, but that it occupies a position between them 

 and the Hystricomorpbine Eodents ; and, if it is desirable for 

 practical purposes to arbitrarily draw a sharp line between the 

 Hystricoraorpha and Myomorpha, Pedetes would fall on the 

 hystricomorpbine side and the Dipodidas on the myomorphine.' 



Ligamentous System, 



The Temporo-maxillary joint has a well-marked lax meniscus ; 

 when the condyle glides forward and backward the meniscus 

 accompanies it, but the hinge-like movements of opening and 

 closing the mouth take place between the condyle and the 

 meniscus. 



The Sterno-davicular joint is formed by the inner end of the 

 clavicle, which is bevelled at the expense of its ventral surface so as 

 to slide doi'sal to the manubrium sterui. This inner part of the 

 clavicle is cartilaginous and is fastened to the sternum by iibrous 

 tissue. 



Acromio-clavicular joint. — The acromion is united to the clavicle 

 by fibro-cartilage and there is no joint cavity here. 



The Coraco-clavicular ligament is well marked and runs from 

 the dorsal border of the clavicle to the coracoid. 



The Shoidder-joint has a lax capsule without any openings, 

 except that for the biceps tendon, or any appreciable thickenings. 

 Both coraco- and gleno-humeral ligaments were looked for, but no 

 trace of them was seen. 



The Elbow is chiefly remarkable for a well-marked crescentic 

 sesamoid bone in the orbicular ligament ; it is attached to the 

 external condyle by the external lateral ligament and gives origin 

 to the supinator brevis ; it articulates with the radius and the 

 humerus, and between it and the olecranon there is a pad of fat. 

 Pronation through 5 of a circle is allowed at this joint when the 

 muscles are removed. 



The interosseous membrane between the radius and ulna is very 

 strong ; above most of the fibres run from the ulna downward and 

 outward to the radius, below they mostly have the opposite 

 direction. There is no synovial cavity between the lower end of 

 the ulna and radius, but the triangular fibro-cartilage is continuous 

 with the interosseous membrane. 



Wrist-joint. — The styloid process of the ulna is large and 

 rounded, and fits into a concavity formed by the cimeiform and 

 pisiform bones. The anterior ligament of the wrist contains ulno- 

 carpal and radio-carpal bands, which both run to the great scapho- 

 lunar bone. The prepollex articulates with the radial extremity 

 of the scapho-lunar (see fig. 1, p. 863), and there is a well-marked 



1 Since writing the above I bave re-read a paper by Mr. Oldfield Thomas on 

 the " Genera of Eodents," P. Z. S. 1S96, p. 1012, and am pleased to find that his 

 views on the position of Pedetes, founded on a study of the skull and teeth, 

 agree exactly with my own. I hope soon to be able to compare the muscles of 

 Anomalurus with those of Pedetes. 



