Shi'iki.ut: Ostkoi.ogv oi' iHr, Hkrodionf.s. 203 



soon subside into the shaft below. A wide valley is between them, 

 and the inner one or procneniial ridge is vertical to the shaft and ex- 

 actly divides the inner surface of it from the anterior. 



All about the head of the tibia the articular summit projects over 

 with its broadly rounded margins. 



The " fibular ridge" extends down the tibial shaft on its outer side 

 but a comparatively short distance. It begins above at a point o])po- 

 site where the ectocnemial ridge merges into the shaft. Behind, a 

 longitudinal concavity fairly defines its extent from the ])OSterior sur- 

 face of the tibia ; in front, the anterior surface of this fibular ridge lies 

 in the same plane with the anterior surface of the tibial shaft. 



From proximal to distal end his shaft is as straight as any long bone 

 that I am familiar with ; it is only just before we arrive at the con- 

 dyles below that we notice the slightest disposition in the world to 

 bend backwards. 



For its entire length behind, the surface is cylindrical ; this is entered 

 into by both the lateral aspects, while anteriorly it is flat, and only 

 round at all for a limited part of the shaft about at the junction of mid- 

 dle and up])er thirds. This flat anterior surface above looks directly 

 forwards, and this is the case also above the tendinal bridge, but as we 

 ascend the shaft from this latter point, it gradually turns towards the 

 outer aspect, when finally it is limited by a raised line th-at descends 

 on this side from the fibular ridge, and merges at last into that part of 

 the shaft which is subcylindrical, at junction of middle and upper 

 thirds. 



At the distal extremity, the shaft enlarges but very slightly, and just 

 sufficient to afford a base for the condyles, which here project in con- 

 sequence well out in front of it, both before and behind, more par- 

 ticularly in the former direction (Fig. 24). 



The " tendinal bridge," though present, is not nearly so well devel- 

 oped as in some other birds, and in my specimen of Nycticorax a 

 "bird of the year," it is not united in the middle, it being simply 

 represented by a triangular process on either side, with their bases in 

 the margins of the excavation, and their ai)ices opposite and nearly 

 touching each other. A tubercle occurs above the outer condyle at a 

 point where this bridge arises on that side. This is its lower origin, 

 as it spans the tendinal groove rather obliquely. 



The inter condyloid depression is wide, deepest in front, to become 

 narrower and shallower behind, where it ceases as the shaft commences. 



