16 THE NECTURUS 



much cartilage remains in the limbs, especially at the ends 

 of the bones. 



The humerus is a straight bone with a crista on the 

 ventral side for the insertion of muscles. These cristse 

 often mark such insertions. The radius and ulna are not 

 much differentiated and do not resemble the bones of the 

 higher tetrapods. They have undergone little specializa- 

 tion and are rather crude in their structure. The ulna 

 is marked by an olecranon process. 



The hand has but four digits, the first having been lost. 

 The carpalia consists of six or seven bones; an ulnare, in- 

 termedium and radiale comprise the proximal series; the 

 median series consists of a single or double centrale ; while 

 the distal series is made up of three bones, one of which 

 probably represents two fused elements. 



The fingers are considered to be *2-3-4-5 and the phalan- 

 geal formula **3-3-4-3. Do the fingers have nails? 



The femur has large cartilaginous ends with a trochanter 

 on the proximal. Is there much difference between the 

 tibia and the fibula? The tarsalia consists of six or seven 

 bones also ; the proximal series made up of tibiales and the 

 joined intermedium and fibilare; the intermediate series 

 of a single centrale ; and the distal series of three tarsalia. 

 The tarsalia for digits 4 and 5 are joined. The formula for 

 the digits of the foot are *2-3-4-5 and the phalangeal 

 formula is **3-3-4-3. 



Visceral Skeleton 



For the most part the visceral skeleton is composed of 

 cartilage, although some of the basibranchials may be 

 ossified. The median series consist of two basibranchials, 

 the first and second. The hyoid arch consists of hypohyals 



* Refers to the numbers of the digits. 



** Numbers refer to the number of bones in the digits. 



