*9 
OGeological Studies of the Subfamily Ardeincc. 
the pro- and ectocnemial ridges are but moderately developed, and 
^ ery soon subside into the shaft below. A wide valley is between 
them, and the inner one orprocnemial ridge is vertical to the shaft 
and exactly 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” ex¬ 
tends down the tibial shaft on 
its outer side but a compara¬ 
tively short distance. It begins 
above at a point opposite where 
the ectocnemial ridge merges 
into the shaft. Behind, a lon¬ 
gitudinal concavity fairly de- 
Fly. JZ. fines its extent from the poste- 
Fig, 31— Left lateral view ot sternum of Ardea rior Surface of the tibia; ill 
candidissima. Life size from nature. . _ _ 
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 this shaft is as 
straight as any long bone 
that I am familiar with ; 
it is only just before we 
arrive at the condyles be¬ 
low that we notice the 
slightest disposition in 
the world to bend back¬ 
wards. 
For its entire length behind, the surface is cylindrical ; this is 
entered into by both the lateral aspects, while anteriorly it is flat, 
Fig. 32.— Left lateral view of sternum of Nycticorax 
violaceus. juv. life size ; from the same specimen as 
former figures used for this bird. 
and only round at all for a limited part of the shaft about at the 
junction of middle and upper 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, where finally it is 
limited by a raised line that descends 011 this side from the fi- 
