402 PROFESSOR OWEN ON THE GENUS CNEMIORNIS. 



Cnemiornis are seen in the development of the ectocnemial and more especially of the 

 procnemial plates ; the extensor-tendinal canal is more strictly medial in Cnemiornis, 

 and the fore part of the inner distal condyle is less produced and less compressed. 

 The gastrocnemial tubercle is wanting in Aptornis, as in Dinornis. 



Fibula. 



The fibula (PI. LXVI. fig. 6), about 6 inches in length, shows the usual subcom- 

 pressed, convex head, with an articular surface, about 14 lines long by 4 lines broad, 

 slightly curved backward : the head is slightly hollowed on the inner side, slightly 

 convex externally ; the shaft gradually contracts to the usual pointed termination about 

 two-thirds down the tibia ; it shows the broad, rough, articular surface for the tibia on 

 the tibial border, and two rough tuberosities for tendinous insertions (u, v) on the 

 outer side of the bone. 



Metatarsus. 



The metatarsal (PI. LXVII. figs. 1^), which equals in length that of Dinornis 

 geranotdes (ib. figs. 5 & 6), has less than two-thirds its breadth, but almost equals it in 

 fore-and-aft extent of the proximal end, owing to the greater development of the 

 calcaneal ridge, which is perforated as in Aptornis. The inner condylar cavity (i) is 

 much less extended from before backward ; the anterior intercondylar prominence (r) is 

 broader and more produced : the calcaneal process extends downward, as a low ridge, 

 to within an inch of the distal trochlea ; the calcaneal canal is 10 lines in length, and 

 4 lines in long diameter. The surface, sloping to the outer condyle, is excavated by three 

 well-marked longitudinal grooves, increasing in width as they approach the outer con- 

 dyle (e) ; the antero-posterior canal, between the outer and middle metatarsal, opens 

 behind at the end of the outermost groove ; that between the middle and inner meta- 

 tarsal opens behind upon the inner side of the base of the calcaneal process ; the trans- 

 verse section of the middle of the shaft is subtrihedral, not transversely oval as in 

 Dinornis ; the inner trochlea {ii) is not produced lower than the outer one (iv) ; the 

 middle trochlea (m) is narrower in proportion to its length, and less produced forward ; 

 in each trochlea, and especially the outer and inner ones, the longitudinal canal is 

 deeper than in Dinornis ; the interspace between the outer and middle trochlete is the 

 widest, not, as in Dinornis, narrowest. The posterior boundary of the middle trochlea 

 is more prominent, projecting further back beyond the shaft than in Dinornis. As 

 compared with Palapteryx, the metatarse is longer in proportion to its breadth ; the 

 calcaneal process in Aptornis is shorter, more prominent, and more widely excavated ; 

 there are no tendinal grooves on its outer side ; the posterior ridge is not continued 

 from it, and is nearer the inner border of the shaft ; the inner trochlea is not produced 

 so low as the outer one in Aptornis, and there is an antero-posterior canal above the 

 interspace between the outer and middle trochleas. 



