^74 ZOOLOGY SECT. 



pubes and ischia of opposite sides meet in ventral symphyses, but there is no 

 obturator foramen. Humerus and femur are both short, and the rest of the 

 bones of the limb are disc-like or polyhedral. The phalanges are numerous, and 

 are usually in more, sometimes in fewer, than the usual five series. The teeth 

 are not in separate sockets, but set in a continuous groove. 



The Ichthyopterygia are of Mesozoic age, ranging from the Upper Trias to 

 the Upper Cretaceous. Geographically their remains have a very wide 

 distribution, having been found not only in Europe and North America, but in 

 the Arctic Regions, in India, Africa, Australia, and New Zealand. 



DlNOSAURIA. 



This order comprises a vast number of terrestrial Reptiles, some of gigantic 

 size (up to over 100 feet in length), of lizard-like or bird-like form, some 



FIG. 1016. Iguanodon bernissartensis. One sixtieth natural size. co. coracoid ; is. 

 ischium ; p. pubis (pectineal process); pp. post-pubic process (pubis); sc. scapula ; 1 IV, 

 17, digits. (From Zittel, after Dollo.) 



approaching Birds in certain features of their structure, others coming nearer 

 the earliest fossil Crocodiles. The surface was in some covered with a bony 

 armour, sometimes armed with long spines. The fore- and hind-limbs were in 

 some equally developed ; in others the hind-limbs were much more powerful 

 than the fore-limbs, and in many their structure appears adapted to a bipedal 

 mode of progression (Fig. 1016). 



The centra are in general amphicoelous, but vary greatly. The sacral region 

 usually comprises 3 to 6 vertebrae. The thoracic ribs have double heads. 

 Abdominal ribs are sometimes present. The sternum was incompletely ossified, 

 and an episternum is absent. There is no parietal foramen. There are 

 complete upper and lower temporal arches, and the fossa is divided into upper 



