HEAD-MQSOLES IN GALLUS AND OTHER SAUROPSIDA. 513 



end left — as a stump^ wliicli Parker (who, however, did 

 not see the earlier stage) erroneously homologised with the 

 "pedicle " in the frog. 



phar 



3 enceph dorceph ccti 



phar I tr sen 



Text-fig. 2. — Coronal section through embryo of Gallus, with 

 14 trunk somites ; outside the dorsal aorta, on either side, is seen 

 the upper lateral part of the pharynx (cp. text-fig. 3), and outside 

 this the upper part of the dorsal cephalic ccelom, wliich is con- 

 tinuous behind with the first trunk somite. (For explanation of 

 lettering see p. 555.) 



In all the Sauropsida, consequently _, there is a long ptery- 

 goid process to the quadrate in early stages of development. 



vent ceph cwl 

 . . tr art 



hypobi spl meso 



Text-fig. 3 — Transverse section through embryo of Gallus, with 

 18 trunk somites. (For explanation of lettering see p. 555.) 



In SphenodoU;, Lacertilia vera, Rhiptoglossa, and Croco- 

 dilia this pterygoid process has a processus ascendens, or epi- 

 pterygoid, which is developed very early in Sphenodon (vide 

 Howes and Swinnerton), late in the Alligator (text-fio-. 22^ 

 p. 527). 



