852 AMPHIBIA. 



The humerus (figs. 42 and 42 a) . — The head of the humerus is slightly oval and 

 continuous with a prominent anterior ridge, along which the articulating surface is 

 prolonged for one-half of its length. This ridge fits into the anterior notch of the 

 glenoid cavity. There is a very prominent process behind for the attachment of 

 muscles to the hinder margin of the coracoid, behind and below the glenoid cavity. 

 Viewing the humerus in front, the upper half is seen to be flattened laterally 

 and the lower half antero-posteriorly. The result is, that the largest axis of the 

 head is in the last-mentioned direction. There is a deep pit on the radial condyle 

 immediately above the capitellum, and an olecranon fossa on the back of the bone 

 above the trochlear articulation. Regarding the humerus in profile from the 

 inner side, it is observed that the radial articular surface projects prominently 

 forwards, while viewed anteriorly it is longitudinally oval. The trochlear surface 

 is narrower in front than behind. The external and internal supracondyloid 

 prominences are well marked. 



The radms (fig. 43) lies obliquely across the arm, with the ulna posterior 

 and external to it. It is a short bone with a broad carpal extremity, articulating 

 with two carpal bones (c and d) and the ulna. The head is rounded with a cup- 

 shaped articular facet, which forms a large sigmoid articular cavity along with a 

 concave articular surface on the head of the ulna. 



The ulna (fig. 43). — The humeral articulation of the ulna is slightly concave, 

 and the radial facet is immediately below it. The inner side of the former is 

 folded over as it were on its inner side to form a small articular surface correspond- 

 ing to the trochlear facet. 



The carpus (fig. 43)^ consists of seven bones, of which only two are in contact 

 with the radius and ulna. The bone in contact with the ulna appears to be a 

 united os ulnare and os intermedium. A large, almost round, os centrale occupies as 

 usual the centre of the carpus, in contact with all the bones of the carpus. 



The pelvic arch (fig. 44) is attached by the sacral rib in the usual manner. 

 The ilium is directed downwards and forwards, and is narrowed and slightly con- 

 tracted in its middle, with either end feebly expanded. Its lower extremity 

 forming the upper border of the acetabulum has a prominent tubercle on its outer 

 and anterior margin, immediately above the acetabulum, facing a rather large 

 process on its ischial side. The ilium, below the tubercle, forms part of the aceta- 

 bulum, which has only two borders, an upper belonging to the ilium, and a lower 

 to the ischio-pubis. The anterior and posterior borders are closed in by strong 

 membranes. The ischial process of the acetabulum is separated from the upper 

 posterior angle of the ischium by a deep depression in the position of the lesser 

 siatic notch bounded behind by a prominent process. The free margin of the pubis 

 is bevelled ofE and very thick, and there is the obturator foramen near its internal 

 angle. Two ypsiloid cartilages are found in the usual position. 



' This plate, I regret to say, has not had the original drawings which were made by myself with the ^reat^st care 

 reversed, so that what is right on the plate is left in nature. The figures also, especially of the skull and carpus, have 

 not that distinctness which could have been wished. 



