E. S. Biggs — Brachiosaurus altithorax. 301 



especially conspicuous in its posterior aspect (fig. 2). The great 

 tuberosity is stout and rugose ; its proximal surface meets the 

 lateral margin of the shaft in a pronounced angle. This angle 

 is not produced posteriorly to enclose a fossa as in Iforosaurus. 

 The mesial border below the head is drawn out into a rather thin 

 margin, but roughened for muscular attachment. The deltoid 

 crest is partially broken away, but was evidently prominent. 

 Its base forms, with the anterior surface of the shaft, a broad 

 and shallow concavity. Midway between the deltoid crest and 

 the great tuberosity is a second rugose surface evidently for 

 insertion of other shoulder muscles. The epicondylar ridge is 

 entirely lost owing to the weathering to which the distal end 

 has been subjected. The direction of the bone fiber on the 

 lateral margin indicates that it was quite prominent. All traces 

 of rugosity have likewise disappeared from the articular end, 

 indicating that the humerus was probably some inches longer 

 than it now appears. 



The coracoid is a less massive bone than that of Brontosaurus 

 (fig. 3). It is elongate antero-posteriorly, rounded below and 

 straight at the coraco-scapular suture. The glenoid articular sur- 

 face is directed outward as well as forward, a feature noted in no 

 other Sauropod genus: The anteroinferior surface is thick and 

 rugose near the glenoid cavity, from which it is separated by a 

 narrow notch only. The inferior border becomes gradually 

 thinner and its rugose .character disappears midway between the 

 glenoid cavity and the anterior scapular border. The marginal 

 concavity noticeable in the specimen at this point is partially 

 due to crushing from contact with the head of the humerus 

 while in the matrix. 



The femur is well preserved though somewhat compressed 

 antero-posteriorly (Hg. 4). Regardless of its great length this 

 bone is quite as stout in the shaft as that of Brontosaurus, 

 though the articular ends are proportionately less expanded. 

 The lateral surface of the shaft has a prominent convexity one- 

 fourth of its length below the great trochanter. A marked 

 rugosity, possibly for the insertion of one of the gluteal 

 muscles, extends downward from the great trochanter to this 

 point. The fourth trochanter* forms a rugose prominence on 

 the posterior margin of the shaft, as in all of the Sauropoda. 



The presacral vertebrae are of the pronounced opisthocoelian 

 type. They are distinguishable from other Sanropod genera 

 by the unusual length of their centra. This, in the first pre- 

 sacral, is slightly greater than the breadth ; it gradually 

 increases in the succeeding members of the series until at 

 the seventh it exceeds the breadth by one-fourth. The centra 



*Dollo, Bull. d. Mus. d. Hist. Nat. d. Belgique, Mars, 1883. Osborn, 

 Memoirs of Am. Mus. of Nat. Hist., Part V. 



