XIII 



l'ilVLl]\r CHORD.ATA 



ri75 



ami litwci parts liy a har toriiu;.! tioiii llie piisltiontal aiiil snuainosal. Hcto- 

 pterygoids are present. 'J'lie (puuliatc is Hnnlj' Hxeil. lii the pectoral arch tlie 

 scapula is vei'y largo, the coracoid small, and the pro-coracoid and clavicle 

 al>scnt. 'I"hc pubis in sonic Dinosauiia has a remarkable slender prolongation 

 (Fig. 1010, pp.) running do\vn\\ards and backwards from the body of the bone 

 parallel with the ischium, an arrangement not found elsewhere except in Birds ; 

 a pubic symphisis does not always occui-. In certain points in the structure 

 of the iiinddind) itself some of the Dinosauria also bear a resemblance to liirds. 

 The teeth, which are usually comi)resstd and may liave serrated edges, arc 

 sometimes placed in sockets, sometimes in grooves. 



Iguanodon (Fig. lOlG), one of the best-known genera, attains the lengtli in 

 the case of one species of over 30 feet. Tiie limbdjoncs are iiollow. Tlic 

 ischium and pul)ic process are long and slender, and inclined backwards and 

 downwards parallel to one another. The liind-foot was diijifujrade, i.e., the 

 weiglit was sup])orted on the phalanges of the digits, and the elongated meta- 

 tarsals, which ^^•cre inunoNal))}- li.ved, liad a nearly vertical position as in Birds ; 



B 



Fig. 1017.— Teeth of Iguanodon mantelli. A, frum the inner, Z>, from the uutcr side. 



(Kr^iUi Zittel, after MantelL) 



the fore-limbs are relatively small, and fossil footprints that have been found 

 indicate that the animal supported itself habitually in a half-erect posture like a 

 Kangaroo, with the fore-limbs raised from the ground. The teeth (Fig. 1017) 

 are of a remarkable shape, flattened and with serrated edges, sometimes with 

 vertical ridges which may l)e serrated. The Dinosauria range from the TrtaS' 

 to the Upper Cretaceous, and were most abundant in the Jurassic and Wealden. 



Pterosatria. 



/ 



The Pterosauria or Pterodactyles are perhaps even more reniarka))le modifica- 

 tions of the reptilian type than any of the orders that have been hitlierto alluded 

 to. The chief peculiarities in the structure of these Reptiles were associated 

 with a flying mode of locomotion, the organs of flight being, as in the Bird and 

 the Bat, the fore-limbs. In the Pterodactyles (Fig. 1018) the last digit on the 

 ulnar side of the manus is enormously prolonged and thickened, and supported a 

 web of skin (Fig. 1020) which extended backwards to the hiud-limbs and the 

 tail. Most of the bones are hollow, and have pneumatic foramina as in Birds 



A A 2 



