1890.] HELODERMA SUSPECTUM. 227 



millimetres long. At the middle of this, upon its dorsal aspect, is 

 found H small pit that has the appearance of an incompleted foramen. 

 This character is constant. 



Both the radius and ulna long retain, at their distal and proximal 

 extremities, the evidences of the epiphysial sutural traces. Sub- 

 cylindrical in form, the shaft of the radius is but very slightly bent, 

 and its enlarged distal end is moulded to articulate with the radial 

 ossicle of the carpus. Its proximal extremity is also enlarged, cup- 

 shaped at its summit, and flattened at the ulnar aspect of its head 

 so as to be brought close against the corresponding extremity of 

 that bone when the skeleton of the arm is properly articulated. 



The ulna, nearly as large as the radius in point of size, has a 

 compressed shaft, with a very conspicuous, semiglobular, articular 

 condyle at its distal extremity. At the other end of the bone the 

 olecranon is well-developed, and a " greater sigmoid cavity " hand- 

 somely excavated. What is interesting here is the fact that no 

 " lesser sigmoid cavity " is formed to admit in articulation the head 

 of the radius, which latter is placed at the expense of a flattening in 

 order to articulate with an apposed flat surface on the ulna, which 

 occurs at the site of the " lesser sigmoid cavity " as it is presented 

 to us in anthropotomy. Thus it will be seen that a sliding movement 

 is admitted of here, but not a rotary motion on the part of the 

 head of the radius, as is the case in many of the higher Vertebrata. 



Five carpalia represent the distal row of ossicles in the wrist of 

 Heloderma, while proximally we find the ulnare, the radiale, and a 

 centrale. Careful search, aided by a good lens, failed to discover 

 any evidences whatever of the presence of an intermedium, much 

 less the vestiges of any rudimentary digit. In a previous section, 

 the large sesamoid that occurs in the great flexor tendon as it passes 

 over the carpus has already been described ; and ligamentously 

 attached to the outer side of the ulna is a large pisiform. As to 

 articulations, two of the carpalia extensively articulate with the 

 ulnare and with each other, while the inner one of the two is in 

 contact extensively with the middle ossicle of this distal row. This 

 last-named one in turn engages the entire inner surface of the ossicle 

 of the carpalia upon its radial side, v/hile its proximal apex comes 

 slightly in contact with the centrale. Number four of the carpalia 

 engages the entire distal surface of the centrale, but barely touches 

 the last ossicle of the distal row upon the radial side. This one is 

 devoted to the radiale and also articulates with the centrale. Proxi- 

 mally, the centrale articulates with the ulnare and radiale. Finally, 

 it is hardly necessary to mention that the carpalia, as a rule, eacli 

 engage a metacarpal distally, while radiale and ulnare articulate 

 with the radius and ulna, respectively. 



The joints of the several digits of the manus remind us considerably 

 of the corresponding parts as we find them in the toes of small 

 ordinary existing birds, more especially the distal ones. Counting 

 the claw in each case, we note that the first finger upon the ulnar 

 side possesses three joints ; the next one to it has five ; the middle one 

 has four ; the next one, radiad, has three j while, finally the radial 



