Shufeldt: Osteology of Lasiopyga and Callithrix. 73 



upper part, and gradually shallowing and narrowing as the lower angle 

 is approached. The acromion process is large and strong and only 

 slightly bent, while the smaller coracoid process is straight, flat on its 

 glenoidal and outer surfaces, and joined to its base at a right angle. 

 The scapular neck is well defined, and the articular surface for the 

 humeral head of the bone of the arm is pear-shaped with the larger 

 end below. The subscapular fossa of the anterior aspect is smooth 

 throughout, but generally exhibits a shallow groove running longi- 

 tudinally from below the neck almost to the inferior angle. 



The Humerus. Among the higher races of men the shaft of the 

 humerus is normally always straight, while in Lasiopyga griseoviridis its 

 shaft is not only somewhat twisted upon itself, but very decidedly 

 curved for its entire length; the concavity of this curvature, extending 

 from the head to the internal condyle, is along its inner aspect, the corre- 

 sponding convexity being down the other side of the bone. This curva- 

 ture is less evident in the shaft of the humerus in Lasiopyga callitrichus, 

 while in Callithrix jacchus the humeral shaft is almost straight. It 

 is a strong, big, heavy bone in Lasiopyga with a large, semiglobular 

 head, the upper surface of which is on a level with the tuberosities. 

 We find the nutrient foramen at the juncture of the middle and lower 

 third of the shaft, above the internal condyle in Lasiopyga; while in 

 Callithrix it is just below the head at the upper end of the bone. 

 Lasiopyga has the internal condyle but very moderately produced, 

 while the marmoset has it very conspicuously produced; and again, in 

 the first-named genus, the outer crest of the trochlea for the ulna is very 

 sharp, prominent, and produced distad; the trochleae are in the same 

 plane in Callithrix. The olecranon fossa in Lasiopyga is always pierced 

 by a large circular foramen, which does not occur in my skeletons of 

 Callithrix, though the bone is quite thin at the site. The usual 

 grooves for muscles and nerves are present, the musculo-spiral gioove 

 being particularly well marked in Lasiopyga, in which genus no part 

 of the shaft can be said to be cylindrical, so pronounced are its borders 

 and the longitudinal grooves between them. No such distinctive 

 features as either an anatomical or a surgical neck exists in the humeri 

 of these apes, and in Lasiopyga the head of the bone does not unite 

 solidly with the shaft until comparatively late in the life of the indi- 

 vidual. It has an extreme length in L. griseoviridis of 12.3 cm., in 

 L. callitrichus of 11 cm., and in Callithrix of 4.3 cm. 



The Radius. In Lasiopyga only the proximal fifth, including the 



