20 Shufeldt, Osteology of Orthovhamphus maenirostvis. f ,^f"|u]y 



on the shaft. The pophteal depression on the posterior aspect 

 distally is unusually deep and extensive, and it is hounded 

 internally by a sharp and conspicuous crest, which extends up the 

 shaft from the condyle. One finds the usual fibular cleft on the 

 outer condyle, which is here deeply sculpt with prominent sides. 

 Distally, the internal condyle supports a rather large, sub- 

 triangular flat facet, which in Hfe articulates with a perforated 

 pad of cartilage resting on the summit of the tibio-tarsus. There 

 is a distinct pit on the outer side of either femoral condyle, and 

 these are for the insertion of the lateral ligaments. 



At the knee-joint there is a small patella, which is broadly 

 cordate in form, it being broad above where it is transversely 

 concaved, with otherwise more or less sharpened borders. 



From one end to the other, the tibio-tarsus is a perfectly straight 

 bone, smooth, and of nearly cylindrical form. The non-extensive 

 " fibular ridge," about a centimeter and a half long, commences 

 at a point about a centimeter below the head. The summit, at 

 right angles to the long axis of the bone, is marked with the 

 usual elevations and depressions to accommodate the large 

 femoral condyles. Above this surface rises the rather low 

 cnemial crest, with both ecto- and ento-cnemial projections well 

 developed. The first is the smaller of the two, and points directly 

 outwards from the end of the bone, the second, thin and quadri- 

 lateral in outUne, is directed anteriorly, being placed a little 

 obliquely on the shaft, with its supero-external rounded angle 

 outermost as well as innermost, with respect to its distance from 

 the head of the bone. This latter projects beyond the shaft all 

 around, until it arrives at the fibular articulation, where quite 

 a valley occurs between its termination and the ecto-cnemial 

 process. 



Distally, the rather small condyles are both reniform in outline, 

 with raised borders. Both anteriorly and posteriorly they 

 terminate abruptly on the shaft, not feathering away upon it as 

 in some birds. An " osseous tendinal bridge " is present 

 anteriorly, spanning the tendinal groove. To the outer side of 

 its proximal entrance there occurs a minute foramen. 



Orthorhamphus possesses rather a small and slender fibula ; it 

 articulates with the outer side of the shaft of the tibio-tarsus in 

 the usual manner. This is here very close with the entire length 

 of the tibia, with which bone it fuses at its lower end, at a point 

 rather below the middle of the shaft. 



Coming to the tar so -metatarsus (Plate VI., fig. ii), it will be seen 

 that the bone presents no curvature whatever, the entire shaft 

 being perfectly straight between the two extremities. Anteriorly, 

 it is conspicuously grooved longitudinally from one end to the 

 other, the gutter being deepest down the proximal moiety, and 

 becoming graduahy more and more shallow down the cUstal half, 

 till it deepens again between the middle and outer trochlea;, in 

 which latter narrow groove we find the foramen for the anterior 

 tibial artery. Both sides of the bone are fiat, while posteriorly 



