122 INSECTIYORA. 



the forward folding of the post-scapular border. The surface between the coracoid 

 border and its posterior ridge forms a long, oval, concave area, with the surface 

 behind it defined posteriorly by the meso-scapular groove shelving down from 

 before backwards. The surface between the groove and the ridge of the glenoid 

 border is flat. 



The clavicle is convex from behind forwards and concave from above downwards. 

 A short ridge marks the anterior surface close to the pre-sternal head of the bone with 

 a corresponding concavity above it. The acromial head of the bone is bent slightly 

 backwards, and is flattened and dilated at its extremity. 



The humerus is elongated and cylindrical. The articular surface is irregularly 

 rounded. The internal tuberosity is small and much separated from its fellow by a 

 shallow bicipital groove. The external tuberosity is moderately large, and is more or 

 less continuous below with the deltoid ridge, which arches upwards, backwards, and 

 outwards, to terminate immediately below the head of the bone on its external 

 aspect. The deltoid ridge begins a little above the middle of the bone as a sharp, 

 laterally compressed ridge, projecting slightly forwards, but not much beyond the 

 surface of the shaft below it. The ecto-condylar ridge is not prominent, and it 

 terminates below the level of the deltoid attachment, but no groove for the musculo- 

 spiral nerve can be detected. The internal condyle is little more than half the 

 breadth of the trochlear surface, but the margin of the bone above it is perforated 

 by a supra-condylar foramen of considerable size. The acromial fossa is not so 

 deep as its fellow in front, and the two are separated from each other by a plate of 

 bone as thin as the finest tissue paper. 



The radius has an outward and forward curve which begins below the process 

 for the attachment of the biceps flexor muscle, and is continued as far as the 

 middle of the bone, while the direction is inwards, so that the two extremities of the 

 bone are in the same line. 



The ulna is more or less laterally compressed, and its anterior margin forms a 

 sharp ridge which expands from behind forwards a little above its middle, so that it 

 comes into close contact with the ulna to such an extent that the two bones at first 

 sight, in some specimens of T. helangeri and T. ellioti, appear to be almost united 

 in that region. There is an open space between the two bones above and below 

 that part, but below that again they are in close contact. On both aspects 

 the ulna is concave external to the anterior ridge, but the concavities stop 

 short a Httle way above the inferior extremity. The internal concavity runs from 

 the coronoid process anteriorly, and the external from the upper margin of 

 the sigmoid cavity. The olecranon is produced considerably behind the sigmoid 

 cavity, and is marked externally by a groove and superiorly by a depres- 

 sion for the triceps extensor muscle. Its posterior margin is narrow and 

 rounded. 



The carpus has a scapho-lunar bone and an os intermedium with a well-developed 

 pisiform, which, along with the process of the first-mentioned, makes the under 



