OSTEOLOGY. 7 



extends from the glenoid cavity, of which it furnishes more than half, upward and 

 inward, to become ligamentously attacht to the upper end of the first costal plate. 

 The other part of this bone extends from above the glenoid cavity inward and 

 forward, to be attacht by ligament to the entoplastron. This process has been 

 variously interpreted, but here it is regarded as the procoracoid, which has become 

 co-ossified with the scapula. It will be called the procoracoid process. For a dis- 

 cussion of this subject and a list of writers who have considered it the reader is 

 referred to a paper by Max Furbringer in Jenaische Zeitschrift, xxxiv, 1900. 

 The other bone of the girdle is the coracoid. It starts from the glenoid cavity, 

 and proceeds inward and slightly backward, to approach closely its fellow at the 

 midlme. 



The writer regards the chelonian limb as belonging to a relatively primitive 

 type. If the reader will peruse Huxley's chapter on the position of the limbs, in 

 his Anatomy of Vertebrated Animals (Appleton's edition, 1872, p. 33), and com- 

 pare his statements with what he can see in the limbs of a turtle, he will probably 

 agree with the view here presented. The apex of the angle at the elbow, instead of 

 being directed backward, is rather directed forward and upward. There is no 

 crossing of the ulna and radius. 



The humerus of the emyd is rather strongly bent in the plane passing through 

 the axes of the three segments of the limb. The head is directed upward. The 

 strongly developt tuberosities for attachment of muscles, the radial, or lateral, and 

 the ulnar, or medial, are bent toward the lower face of the bone. The ulnar is 

 always the larger. At the distal end of the bone, on the anterior or radial side, is a 

 passage for the radial nerve, the ectepicondylar foramen. 



Of the two bones of the lower arm the radius is the smaller. It has a shallow 

 cavity at the proximal end that meets the articular end of the humerus. Its distal 

 end is expanded and articulates with the intermedium and the radiocentrale of the 

 carpus. The ulna is the stouter bone, is flattened, has the suggestion of an olecranon 

 process, and articulates distally with the intermedium and the ulnare. 



The carpus is simple. Besides the bones already mentioned as belonging to the 

 carpus, there is another in the proximal row, on the outer side of the ulna. There 

 are 5 bones in the distal row, but sometimes the fourth and the fifth are co-ossified. 

 There are 5 metacarpals, each of medium length. The digits are 5 in number, the 

 first and the fifth the shortest. The first digit has 2 phalanges, the others 3 each, 

 exactly as in the Mammalia. 



The pelvis is broad and short, and each half is composed of 3 bones, all of 

 which take part in the formation of the acetabulum. The ilium is expanded antero- 

 posteriorly above and is articulated with the outer ends of the sacral ribs. The 

 middle of the bone is slender. Each ischium has a posterior process which rests 

 on the xiphiplastron and an anterior process which runs forward to join the pubis 

 of its side. There is thus produced on each side a large heart-shaped fontanel, 

 the ischio-pubic foramen. Each pubis has a lateral process which rests on the 

 xiphiplastron. The pubis is prolonged forward considerably, and between the two 

 there is a median notch which in life is filled with cartilage, the prepubic; but this 

 does not become ossified. 



The femur resembles considerably the humerus; but it is a longer bone and 

 there is no perforation corresponding to the ectepicondylar foramen. The head is 

 larger and of different form. The trochanters are of about the same size and the 

 digital fossa separates them far down. The tibia is a stouter bone than the fibula. 

 Its upper end is the larger and presents a large surface for articulation with the femur. 

 The lower end has a saddle-shaped articular surface to join the large bone forming 



