262 PROFESSOR OWEN ON CNEMIORNIS. 



which is not definable by reason of fracture. The breadth of the anterior articular 

 surface of the centrum is 1 inch 7 lines ; its height at the middle is but 5 lines ; this 

 bilobed character is more strongly shown in the next. 



The second dorsal presents a structure which seems not to have hitherto been noted 

 in birds. Besides the median process (hypapophysis) (PL XXXVI. fig. 11, hy) from 

 the fore part of the under surface of the centrum, there is a pair of processes (ib. 

 ib. hi, hi) from the sides of that part of the centrum, which part extends vertically 

 below the anterior articular surface (ib. fig. 11, c, c) for an extent of from 2 to 5 lines, 

 and is festooned below by the emarginations between the origins of the median {hy) 

 and lateral [hi) inferior processes. This character is rudimentally indicated in the 

 first dorsal vertebra of Cereopsis (ib. fig. 1 3, hy, hi) ; the processes {hi) are broader and 

 more transversely extended in Tachyeres (ib. fig. 14). The articular surface for the 

 tubercle of the rib is supported in Cnemiornis by a distinct process (ib. figs. 11 & 12, dt) 

 from the under part of the base of the diapophysis {d). The process is feebly indi- 

 cated in Cereopsis and Tachyeres (ib. fig. 14, dt). The length of the second dorsal 

 vertebra in Cnemiornis from the postzygapophysis {z') to the broken end of the mid 

 hypapophysis {hy) is 2 inches 4 lines. The length between the same points of the 

 corresponding vertebra in Cereopsis is 1 inch. The rib has a short, straiglit sternal 

 portion tied by ligament to the anterior small tubercle of the costal border of the 

 sternum. 



In the third dorsal (PI. XXXVI. figs. 15, 16) the hypapophysis {hy) extends its 

 base the whole length of the centrum, and curves forward as it narrows to a trituber- 

 culate end, the mid tubercle projecting beyond the lateral pair (ib. fig. 16, hi, hi), and 

 also beyond the vertical parallel of the joint between' the third and second dorsal 

 centrums. The upper spine (ib. fig. 15, ns) also curves forward, its anterior apex 

 reaching the same vertical parallel as that below {hy). One or two longitudinal ridges 

 strengthen the neural spine near its summit. The hypapophysis of the fourth dorsal 

 (ib. fig. 17, hy) has a less extensive base, but equal length ; it is also curved forward, as 

 is the neural spine ; but this is longer, and gains more antero-posterior breadth toward 

 its truncate summit. 



The fifth and sixth free dorsals cease to develop hypapophyses ; their neural spines 

 continue to gain in antero-posterior breadth. The principal pneumatic aperture in the 

 dorsal vertebrae of Cnemiornis is at the base of the diapophysis (ib. figs. 15, 17, d), 

 between the articular surfaces (ib. pi and dt) for the bifurcate head of the rib ; in the 

 cervical vertebrae it is at the base of the neural arch. 



The ribs, both vertebral and sternal, increase in length ; and epipleural appendages 

 are attached to the former from the second to the seventh pair. 



The chief things notable in the dorsal vertebrae of Cnemiornis, as compared with 

 Cereopsis and existing Anserines, are the great breadth of the centrum in proportion 

 to the length, the minor fore-and-aft extent of the neural spines in proportion to their 



