350 



Georgina Sweet : 



Specimen B of Hyla aurea, 

 having four arterial ai'ches in 

 the adult. 



(Reference letters as in Text- 

 figure 1). 



f/cZ 



Specimen of Hyla aurea, 

 having four arterial arches in 

 the adult. 



(Eeference letters as in Text- 

 figure 1). 



ffG 3 



between the systemic and pulmo-cutaneous arches, and arises 

 from the pidmo-cutaneous arch, ch)se to its origin from the 

 right or left half of the truncus arteriosus. It then runs out- 

 wards between the muscles, M. petrohyoideus II. and III., and 

 on one side (R) of individual A, it coils about considerably 

 dorsal to M. petrohyoideus III. and ventral to the systemic 

 arch, which crosses the path of this vessel on its way round the 

 oesophagus. In both A and B, and on each side, the extra arch 

 opens into the cutaneoua artery soon after the latter leaves the 

 pulmo-cutaneous arch. In individual A (Text figure 1) the extra 

 arch divides into two vessels, one coiling round to meet the 

 cutaneous artery, the other nmning forwiu'ds and outwards to 

 the skin. In the other individvud li (Text figure 2) the extra 

 arch does not coil, but riuis almost straight into the cutaneous 

 artery, giving off just before this union, a small vessel which 

 runs inwards to the muscles of the laryngeal wall. I was 

 unable to determine whether the systemic also gave off a 



