560 textbook of zoology 



Order Rhincocephalia 



Suborder Sphenodontia (Sphenodon, Tuatara). — The only living 

 representative of this order is Sphenodon punctatum, a lizardlike 

 animal found on a few small islands off the coast of New Zealand. 



It is often called a "living fossil" because many of its anatomical 

 characters are found in no other living reptile. Some of these 

 characters are old, even in relation to many extinct reptiles. The 

 entire brain is said to be smaller than one of its eyes. Unlike all 

 other living reptiles, it has no external copulatory organ. There 

 are ten separate carpal bones present. This is a primitive number. 

 Many other skeletal features indicate a close relation to reptiles 

 of other geological periods. 



The adults usually attain a length of about twenty inches. They 

 are dull yellowish or olive brown in color. A middorsal row of 

 spinelike scales extends from the occipital region to the end of the 

 tail. There are other rows of smaller excrescences along the sides. 

 One of the most interesting features of the animal is its pineal eye. 

 This "third eye" is located in the center of the head between the 

 eyes. It is surrounded by a rosette of small scales and covered 

 by a translucent plate. The nerve from this eye is well developed 

 and passes to the brain through a foramen in the cranium. There 

 are a retina and a cornea in the structure of this organ, but the 

 extent of its function as an eye is unknown. 



The habits of the animal are as unique and interesting as its 

 structure. It lives along the shore in burrows with a small petrel, 

 a shore bird of that region. It is said that the reptile and the bird 

 have special sides in the enlarged chamber at the end of the burrow 

 and neither trespasses on the other's space. The food of these ani- 

 mals consists of insects, spiders, and crustaceans. In captivity they 

 have been known to thrive on a diet of earthworms. They are 

 nocturnal, hiding by day and hunting along the beaches at night. 

 Reproduction is oviparous, about ten eggs being a usual complement. 



Order Crocodilia 



Suborder Eiisuchia (crocodiles and alligators). — This order is rep- 

 resented by about twenty living species. They are found along the 

 coastal plains in our Southern States, southward through Mexico, 

 Central America, and in the warmer regions in South America. In 



