330 The Alligator and Its Allies 



the tail) of this age is shown in Figure 23a. In the 

 head region the section is nearly median, while the 

 posterior part of the body is cut slightly to one 

 side of the middle line. At the tip of the now 

 well-developed snout is seen one of the nostrils {an), 

 cut through the edge ; its connection with the com- 

 plicated nasal chamber (w) is not here seen, nor is 

 the connection of the nasal chamber with the 

 posterior nares {pn). The pharynx {ph), is ante- 

 riorly connected with the exterior through the 

 mouth ijn) and the nares, while posteriorly it 

 opens into the oesophagus {oe)\ the trachea {ta), 

 though distinct from the oesophagus, does not yet 

 open into the pharynx. In the lower jaw two 

 masses of cartilage are seen, one near the sym- 

 physis (mk) and one near the wall of the trachea, 

 doubtless the rudiment of the hyoid. The deep 

 groove back of the Meckel's cartilage {mk) marks 

 the tip of the developing tongue, which here forms 

 the thick mass on the floor of the mouth cavity. 

 Dorsal to the pharynx a mass of cartilage {se) 

 is developing in the sphenethmoid region. This 

 being a median section, the ventricles of the fore- 

 {fb), mid- <ymh), and hindbrain Qih) are seen as large 

 cavities, while the cerebral hemispheres {ch) appear 

 nearly solid, only a small portion of a lateral 

 ventricle showing. The paraphysis {epi) is cut a 

 little to one side of the middle and so does not show 

 its connection with the brain. At the base of 

 the brain the infundibulum {in) is seen as an elon- 



