1890.] EXTINCT BIROS FROM MALTA. -J05 



the complete structural identity of the bones, so that detailed descrip- 

 tion is unnecessary. The characteristic Accipitrine features of this 

 part of the tibio-tarsus are the fore and aft compression of the shaft, 

 the shallow anterior groove, the wide separation of the two condyles 

 on the anterior surface, the extreme obliquity of the bony bridge 

 over the groove for the extensor tendons, and the absence of any 

 tubercle on the bridge itself\ On the posterior aspect of the bone, 

 which has not been figured, the shallowness and great relative width 

 of the trochlear surface are equally characteristic. The rough surface 

 for the articulation of the distal extremity of the long fibula is 

 distinctly seen on the postaxial border of the fossil. The specimen 

 represented in the next figure (Plate XXXV. fig. 1) is the imperfect 

 proximal extremity of a right t'bio-tarsus, doubtless forming a part of 

 the same bone as the preceding specimen. The cnemial crest 

 and external surface of this fragment are somewhat imperfect, but 

 the contour of the portion which remains perfect agrees in all re- 

 spects with that of the smaller tibia of V. vionachus. The greatest 

 transverse diameter of the fossil tibia is 0,030, the corresponding 

 dimension in that of the existing species being 0,025. The total 

 length of the libia of V. monachus is 0,222 ; and if the same pro- 

 portion of breadth to length obtained in the extinct species the 

 total length of its tibia would be 0,266. The fossil tibia may be 

 distinguished from the recent one by the somewhat greater prominence 

 of the bridge (a) over the groove for the extensor tendons, and the 

 absence of the lateral perforation (c) which communicates with the 

 same groove. The great size of this tibia indicates the probability 

 of its owner having belonged to Vultur (or an allied genus) rather than 

 to Aquila, this inference being rendered certain by the following 

 specimens. 



The tarso-metatarsus of the Accipitres is fully as characteristic as 

 the tibio-tarsus, even when, as in the present instance, we have only 

 the distal trochlese to work with. Thus these trochleae approximate 

 more or less closely to the same transverse line, and form a slight but 

 regular curve from side to side. The distal extremity of a left tarso- 

 metatarsus (represented in Plate XXXV. fig. 6) accords so exactly in 

 contour with the smaller bone of Vullur monachus (shown in fig. 7 of 

 the same Plate) that their close affinity is manifest at the first glance. 

 Moreover, in the relative length of the trochleae, and the elevated 

 position of the trochlea for the fourth digit, coupled with the slight 

 lateral expansion of the one for the second digit, the fossil specimen 

 resembles Vultur &nA differs from Aquila. The much shorter tarso- 

 metatarsus of Gypaelus, while approximating to Vultur in the gen- 

 eral form of the trochleae, resembles Aquila in the lateral expansion 

 of the trochlea for the second digit. This specimen is therefore 

 decisive that the fossil form should be referred to Vultur or Gyps. 

 The transverse diameter of the trochlea for the third digit is 0,012, 

 against 0,010 in V. monachus. The Museum also possesses portions 



' By an unfortunate error it is stated in Nicholson and Lydekker's ' Manual 

 of Palaeontology,' ord. ed. vol. ii. p. 1239, tliat the bridge itself, instead of its 

 tubercle, is absent in the Accipitres. 



Proc. Zool. Soc— 1890, No. XXVUI. 28 



