ANATOMY OF MEGAPTERA LONGIMANA. 35 



of the bone and to the distal border of the cartilage. The 

 proximal joint is a cavity for more than the middle half of the 

 breadth of the cartilage, and for the rest is soft connective tissue. 

 Towards the radial side, the line of the joint, in the left paddle, 

 makes a bend with the concavity distal on the radial fourth of the 

 joint ; in the right paddle, it is bifurcated there like the letter <. 

 The distal joint occupies about the middle half of the cartilage 

 and presents a central synovial cavity. It was noticed only on 

 section. The preserved sections show the elliptical synovial 

 cavity of the distal joint concealed on both surfaces, and the 

 proximal joint as a more developed synovial cavity, indicated by 

 furrows on both the flexor and extensor surfaces, but the cavity 

 may be interrupted in part by soft fibrous tissue (fig. 12). As 

 this distal joint would have been overlooked had the surfaces 

 only been examined, we see how the commencement of an 

 additional phalanx, or the existence of a phalanx potentially, 

 may be overlooked. 



In digit IV., after the 7th node, there is a solid cartilage, 2J 

 inches in length by 2 in breadth, which might pass for a repeti- 

 tion of the 7th bone, or of the 8th bone of digit III., but for 

 greater enlargement at its distal end, on the radial side. It is 

 plainly the 8th bone of the digit as yet unossified. Then, 

 with a joint between, comes a narrower cartilage, 2 inches in 

 length by 1 inch in breadth. 



Interpreting these terminal cartilages and their joints, the 

 cartilage and its dividing joint in digits III. and V. might be 

 described simply as the parts of a node in a flattened form, with 

 its rudimentary joint. If more phalanges are to be formed, 

 then the part distal to the joint would be potentially a phalanx 

 and its epiphysis, while the part proximal to the joint would 

 be the distal epiphysis of the as yet distal phalanx. The 

 simplest view is to regard the part between every two joints, 

 or distal to the distal joint, as an element capable of becoming 

 a bony phalanx with its unossified part, or epiphysis, at each 

 end. In digit IV., the first mentioned cartilage represents a 

 phalanx and its distal epiphysis ; the distal cartilage, the same 

 as the element distal to the joint in the terminal cartilage in 

 III. and V. In digit II., in which the great expanded cartilage 

 has two joints, the proximal part may be regarded as the distal 



