( 82 ) 



a specimen 135 mm. long the width of the proximal articular sm-face is 21, uf the 

 distal end 19, and of the middle of the shaft 8. 



Iht- tilnda is greatly expanded at its upper extremity ; opposite the lower end 

 of its union with th^ fibular crest is a large rough surface for the insertion of the 

 biceps cruris. Its lower portion is styliform, and extended to about the commence- 

 ment of the lower third of the tibia. The fibula associated with the tibia of whieli 

 the measurements have just been given is 80 mm. long, and its upper end is 

 13 mm. wide. 



It is in the tarso-^metatarsus that the differences between Diaphoraptei-yx and 

 A phanapteryx are most emjjhasised, that of the former being short and stout, tliat 

 of the latter comparatively long and slender; it has, however, been suggested by 

 Forbes that the tibia and metatarsus described by IMilni'-lvlwards may not belong 

 to the same species. 



As in most rails, the inner glenoid surface is higher than the outer, and there 

 is a prominent intercondylar tubercle; the whole proximal articular surface is 

 considerably more extended transversely than in Aphanapteryx and Ocydromiis. 

 The talon forms apparently a much more prominent mass than in Ajihanapte^'yx, 

 but the sj)ecimen figured by Milne-Edwards is said to be somewhat broken. In the 

 arrangement of the crests it is very closely similar to Ocydroraus in most s])ecimens ; 

 but in some the inner crest is much produced backwards and curves somewhat 

 outward towards the main ridge, while the intermediate one is almost absent. The 

 peculiar hypotarsus of Aptoiiiis, which consists of two high crests meeting posteriorlv 

 and enclosing a large canal, may have originated in this way. On the anterior 

 surface of the bone the two interosseous foramina open at different levels, the inner 

 being the higher ; in many specimens this inner interosseous channel has no aperture 

 on the posterior surface of the bone. On the inner side of the inner foramen there 

 is a well-marked channel for the tendon of the extensor communis digitorum. The 

 inner rugosity for insertion of the tibialis (inticu^ is considerably the larger ; in some 

 specimens the two are completely confluent. 



The shaft of the bone is much flattened from liefore backwards ; there is a very 

 large surface for the attachment of the hallux. There is a large foramen for the 

 adductor of the outer digit. The distal trochleae are very large and set wider apart 

 than in the smaller rails, and even than in Ocydromus, in this respect resembling 

 Aphmapteryx ; the inner trochlea is greatly reflected backwards. 



The whole Iwne diverges from the normal ralhne form in its short stout shaft 

 and its expanded extremities ; in these respects it approaclies the metatarsus of 

 Aptornis, which has been still further modified in the same direction, and differs 

 from our fossil in the form of its talon, in the fact that its glenoidal cavities are 

 nearly at the same level, in possessing a still broader and more flattened shaft, and 

 in the arrangement of the distal trochleae. Owen regarded it as modified for 

 " rasorial " purposes, and \>('r\\iy\-,i^ Diaphorapleryx\r,v\ to a less extent adojited similar 

 habits. 



The length of this bone ranges from 63 to 78 mm. in length, the longest 

 being about 24 per cent, longer than the shortest. The average size of fifty-five 

 specimens was C9 mm. In a specimen 70 mm. long the width of (lie proximal end 

 is 20 mm. and of the distal 21 mm. ; the antero-posterior diameter of I he middle of 

 the shaft (i mm., that from side to side 10 mm. 



In the following table the relative lengths of the femur and metatarsus compared 

 with the tibia in various birds is given, the latter being taken as 100 in all cases : — 



