GIGA^'TIO BIED FEOM LOWER EOCENE BEDS. ]51 



fig. 2) was laid by the side of this cast, the resemblance between them was more 

 striking than one was led to expect from an examination of the figures only. 



The tibio-tarsus of G. parisiensis is intermediate in size between the two more perfect 

 Croydon specimens (PI. XXVIII. fig. 2, PI. XXIX. fig. 7) ; but its condyles are too 

 much brolien to allow of any close comparison of these parts, and the form of the 

 upper end is deceptive on account of its having been crushed and spread out laterally 

 {vide ' Oiseaux Fossiles,' pi. 28). In general form the French and English specimens 

 seem to be much alike ; but the shaft is proportionally more robust in G. parisiensis, 

 and the back of the bone, just above the condyles, is flatter and broader in proportion 

 to the front of the bone, while in the Croydon specimen this hinder region (PI. XXIX. 

 fig. 10) is more rounded, and fails away more towards the outer side. In the Croydon 

 bone also the inner and front part stands out more boldly, where it curves down to the 

 inner tuberosity (PI. XXIX. figs. 7, 8, i.t). The Meudon bone has the lower margin 

 of the supratendinal bridge broken, and consequently one cannot speak of it with 

 certainty ; but the lower aperture seems to be more nearly in the middle, and to look 

 more directly forward than it does in the Croydon specimens ; also the intercondylar 

 depression is much deeper ; this and some other differences, however, are probably due 

 to the imperfection of the French specimen. The groove for the tendon of the peroneus 

 muscle, which is distinctly seen just above the outer condyle in the Croydon bone 

 (PI. XXIX. fig. 7, t.g), is not nearly so well mai-ked in the Meudon bird. 



The tibio-tarsus of Gastornis parisiensis diff'ers, therefore, from that of the Croydon 

 bird in having the sliaft proportionally stouter, the inner condyle not projecting so 

 much inward, the back of the bone above the condyles flatter and broader, the supra- 

 tendinal bridge more nearly central, possibly the intercondylar depression deeper, and 

 little or no groove for the peroneus tendon. 



The Meudon and Croydon femora are both too imperfect for satisfactory comparison ; 

 but it is clear that both have a very prominent crest extending along the front of the 

 shaft, beginning at the trochanter, where it is most strongly developed, and reaching 

 perhaps three fourths the length of the bone, becoming less and less as it proceeds 

 distally. 



Gastornis edivardsii seems to be less like the Croydon bird than does G. parisiensis. 

 The tibio-tarsus of G. edwardsii figured by Dr. Lemoine {loc. cit. pi. 2) is propor- 

 tionally a shorter and stouter bone, and the supratendinal bridge is more nearly in the 

 middle. The Croydon remains give no evidence of the double curvature of the outer 

 side of the bone, a character in G. edivardsii to which Dr. Lemoine calls special 

 attention. The imperfection of our examples renders it somewhat uncertain, but I 

 do not think that they could ever have had this double curvature. 



The second tibio-tarsus figured by Dr. Lemoine {I. c. pi. 6. figs. 4, 5) has the condyles 

 and adjacent parts preserved, and these, although in a general way corresponding with 

 the Croydon specimens, show some important differences. The inner condyle does not 



VOL. XII. — PAKT T. No. 2. — December, 1886. 2 a 



