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Show 1890.] EXTINCT BIRDS FROM MALTA. -105 the complete structural identity of the bones, so that detailed description 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 itself1. O n 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 X X X V . fig. 1) is the imperfect proximal extremity of a right tibio-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 respects with that of the smaller tibia of V. monachus. 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 tibia of V. monachus is 0,222 ; and if the same proportion of breadth to length obtained in the extinct species the total length of its tibia would be 0,266. The fossil tibia m a y 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 trochlea? 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 X X X V . fig. 6) accords so exactly in contour with the smaller bone of Vultur 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 trochlea., 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 and differs from Aquila. The m u c h shorter tarso-metatarsus of Gypaetus, while approximating to Vultur in the general form of the trochlese, 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 M u s e u m also possesses portions 1 B y an unfortunate error it is stated in Nicholson and Lydekker's ' Manual of Paleontology,' 3rd. ed. vol. ii. p. 1239, that the bridge itself, instead of its tubercle, is absent in the Accipitres. P R O C ZOOL. Soc-1890, No. XXVIII. 28 |