The =episternum= (fig. 30, A, 10) is a thin almost circular plate of cartilage much of which remains hyaline. The =omosternum= (fig. 30, A, 11) is a slender bony rod widest at its posterior end; it connects the episternum with the ventral ends of the precoracoids. The =sternum proper= is a short rod of cartilage sheathed in bone; it is contracted in the middle and expanded at each end. It bears attached to its posterior end a broad somewhat bilobed plate of partially calcified cartilage, the =xiphisternum= (fig. 30, A, 13). B. THE ANTERIOR LIMB. This is divisible into three parts, the =upper arm= or =brachium=, the =fore-arm= or =antibrachium=, and the =manus=. All the larger bones have their ends formed by prominent epiphyses which do not unite with the shaft till late in life. Their articulating surfaces are covered by hyaline cartilage. In the =upper arm= there is a single bone, the =humerus=. This has a more or less cylindrical shaft and articulates by a prominent rounded =head= with the glenoid cavity. The distal end shows a large rounded swelling on either side of which is a =condylar ridge=, the inner or postaxial one being the larger. A prominent =deltoid ridge= runs along the proximal half of the anterior surface, and in the male frog a second equally prominent ridge runs along the distal half of the posterior surface. The =fore-arm= consists of two bones, the =radius= and =ulna=, united together and forming the =radio-ulna=. The two bones are quite fused at their proximal ends where they form a deep cup which articulates with the distal end of the humerus, and is drawn out into a rather prominent backwardly-projecting =olecranon process=, which ossifies from a centre distinct from that of the shaft. The distal end is distinctly divided by a groove into an anterior radial and a posterior ulnar portion. The =manus= consists of two parts, the =wrist= or =carpus= and the =hand=. The =carpus=[57] consists of six small bones arranged in two rows. The three bones of the proximal row are the =ulnare=, =radiale= and =centrale=. The =ulnare= and =radiale= are about equal in size and articulate regularly with the radio-ulna. The =centrale= is pushed out of its normal position and lies partly on the pre-axial side, partly in front of the radiale. Of the three bones of the distal row the two pre-axial ones, =carpalia 1= and =2=, are small; carpale 2 articulates with the second metacarpal, carpale 1 with both the first and second. The third bone is large and articulates with the third, fourth and fifth metacarpals, it represents =carpalia 3-5=, with probably in addition the representative of a second centrale. The =hand= consists of four complete digits, and a vestigial =pollex= reduced to a short metacarpal. Each of the four complete digits consists of a =metacarpal= and a variable number of =phalanges=. The first digit, as just mentioned, has no phalanges, the second and third have two, and the fourth and fifth have three.