.S74 



^X)OT/)nY 



SECT. 



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

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

 l)ones 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 sejiarate sockets, but set in a continuous groove. 



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

 the Upper Cretaceous. (ieograpliically tlieir 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. 



DlSOSAt'IilA. 



This order comprises a vast numljcr of terrestrial Reptile-s, some of gigantic 

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



Fig 1010.— Ignanodon bernissartensis, Ouc sixcieth natural size. co. coracoid ; w. 

 ischium ;%.i.ul.is (pectineal frncc^s); pp. i.o.st-imlnc process (pubis); sc. scapula ; I—IV, 

 /— F, digits. (Fruui Zittcl, after DoUo.) 



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

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

 armour, sometimes armed with long spines. Tlie fore- and hind-lindjs Mere in 

 some equally dexoloped ; in others the hind-liinbs were much more powerful 

 tlian tiie fore-limbs, and in many tiieir structure appears adapted to a bipedal 

 mode of progression (Fig. lOlti). 



The centra are in general amphiccelous, but vary greatly. 1'he sacral region 

 usually com))rises 3 to 6 vertebra'. Tlic thoracic ribs have double heads. 

 Al)doi'uinal libs are sometimes present. Tiie 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 



