376 



CROCODILIA. 



The eustachian passages * are surrounded by bone and open close to- 

 gether into the pharynx by a median opening behind the posterior nares. 

 From this opening (Fig. 206) there passes off three tubes, one median and 

 two lateral. The median tube (o) is contained in a canal between the 

 basioccipital and basisphenoid, where it bifurcates into an anterior branch 

 (q) which passes into the basisphenoid, and a posterior into the basi- 

 occipital (r). The anterior branch divides into a right and left canal which 

 open into the tympanic cavity. The posterior also bifurcates and each of 



the canals so formed (s) runs to open 

 into the tympanic cavity by a tube 

 (t), which joins one of the two lateral 

 canals (p) which pass from the pha- 

 "1 ryngeal opening. 



2 



The columella is bony and 

 extends from the fenestra ovalis 

 to articulate with a trifid car- 

 tilage the extra-columellar car- 

 tilage (infra- + extra- + supra- 

 stapedial), which is attached to 

 the tympanic membrane. 



The lower process of this cartilage is 

 continuous with a partly cartilaginous, 



4 partly fibrous cord which lies in a 



20 groove or canal on the hinder surface 

 of the quadrate immediately behind 

 the siphonium, and is connected with 

 the os articulare of the lower jaw. 

 The upper cartilaginous part of this 

 cord is called by Huxley the styloid 

 cartilage. In the embryo this cord 



tor "(Catiwnl^trorfrt*) 4 to^oweusu^al was a continuous cartilaginous con- 

 choanae (after Reynolds). 1 premaxilla ; ne ction between the lower process 

 2 ( maxilla; 3 palatine ; 4 pterygoid ; 5 ... .. ,. , , , 



choanae; 6 transpalatine ; 7 posterior, (mfra-stapedial) of the extra-columel- 

 8 anterior palatine vacuity ; .9 basioc- ] ar cartilage and Meckel' s cartilage, 

 cipital ; 10 median opening of the eusta- 

 chian tube ; 11 jugal; 12 quadrato-jugal ; 13 



quadrate; 20 lateral temporal fossa ; 21 rpVio Tnrnirl r>rmeite nf a rartila 

 vascular channels leading into openings lne n yld COUSlStS C 



ginous body and a pair of partly 

 ossified cornua. 



The lower jaw consists of six bones, the dentary which suturally 

 unites with its fellow at the symphysis and bears the sockets in 

 which the teeth are implanted ; the splenial (operculare), the 

 angular, the surangular, the articular which is pneumatic, and 

 the coronoid. In the long-snouted forms the splenial may take 

 part in the symphysis. 



13 9 10 



FIG 205. Ventral view of skull of analliga- 



Owen, Phil. Trans., 1850; v. Beneden, Arch, de Biologic,. 3, 1882, p. 497r 



