IO 



JEAN DAWSON. 



ventrad to join the oesophagus and water tube. It results that 

 the jaws extend obliquely across the opening from pharynx to 

 water tube so as to intercept anything passing into the water tube. 

 Nothing further can be seen of this apparatus from the pharyn- 

 geal cavity, but if the water tube be opened from the ventral side 

 the velar jaws may be seen in connection with the velar valves 



x: 



FIG. 6. Ventral view of the head of P. tnarimts with the cavity of the water tube 

 and pharynx exposed, a, tongue ; b, oral funnel ; d, velar valves ;/, internal branch- 

 ipores ; /, velar jaws ; s, water tube ; .r, anterior lobe of the tongue. 



which guard the passage between the pharynx and water tube 

 ( Fig. 6). The velar valves (Fig. I,/, and Fig. 6, d) are two 

 semilunar flaps which extend dorso-ventrally, one on either side 



