PROFESSOR OWEN ON THE GENUS CNEMIORNIS. 399 



Sternum. 



The three portions of the sternum of Cnemiornis include the right costal border and 

 process (PL LXIII. figs. 5 & 6), part of the left (figs. 7 & 8), and the middle part of the 

 bone (fig. 9)'. The costal border (c) is 3 inches 6 lines in length, and includes seven 

 articular ridges (h) for the sternal ribs, the last contracting to the form of a tubercle ; 

 and there is also a tubercle of smaller size at the angular beginning of the border. The 

 costal process (d) is quadrate, slightly concave on the inner side, convex lengthwise 

 on the outer side, and smooth, as if for some articulation ; the pneumatic foramina are 

 at the base of this process, on the inner side of the sternum, and are also seen at the 

 costal border, at the interspaces of the articular ridges on the medial side of the base of 

 the costal process. The posterior boundary of what appears to be the shallow and 

 narrow coracoid groove (b) extends from above these foramina mesial, the body of the 

 sternum being broken away from near the base of the costal process. The greatest 

 breadth of the body of the sternum preserved, at the end of the costal border (fig. 5, c, a), 

 is 1 inch 8 lines ; the length of this right portion of the sternum preserved is 4 inches 

 5 lines, and shows no trace of posterior notch ; it is gently convex lengthwise, concave 

 transversely, but in a less degree ; and the fore part of the sternum, for more than an 

 inch behind the costal process, shows a shallow excavation. A smaller proportion of the 

 body of the sternum remains connected with the left costal margin : it cannot, there- 

 fore, be positively affirmed that the keel was absent, but this may be inferred from the 

 thinness of the sternum at the fractured mesial margins (a') of the two lateral portions. 

 From the sternum of Notornis that of Cnemiornis differs in the greater extent and dif- 

 erent direction of the costal border, the greater number of articular ridges, the presence 

 of the costal process, and the much greater breadth of the body of the sternum. 



The middle portion of the body of the sternum (fig. 9) includes a length of 4^ inches, 

 with a breadth of 2^ inches, of that part of the bone. Its thickness does not exceed 

 2 lines at the fore and mid part. It is very feebly convex externally, and correspond- 

 ingly concave on the opposite surface. A pair of shallow muscular surfaces nearly 

 meet at a slightly raised median tract (.s), convex transversely, and from 2 lines to 3 lines 

 across, extending from the anterior fractured margin about 1 inch along the bone, leaving 

 more than 3 inches beyond free from even this feeble indication of a keel. 



Humerus. 

 The humerus (PI. LXVI. figs. 7-10), by its small size, slender proportions, and feeble 

 development of the parts at the proximal end, accords with the characters of the 

 sternum, and indicates the incapacity of the Cnemiornis for flight : the articular head (a) 

 is narrow in proportion to its length, and is not broader or more convex at its 

 middle part, as in birds of flight ; its margin projects posteriorly, but anteriorly falls 

 into a shallow concavity. The inner (ulnar) tuberosity (c) rises above the articular 

 ' These figures have been drawn on the stone, without being reversed. 



