ERRATA 



P. 47. Fig. 7. Delete fig. B, and substitute the accompanying figure. 



arotid 



Systemic 



CdYlLTn 



aortic u 



P. 48. Delete from the full stop after " fully extended " to " below," line 

 33, and read instead: 



" dividing it into a chamber beginning on the ventral side and curving 

 round to the right, the cavum aorticum, and another beginning on the 

 dorsal side and curving round to the left, the cavum pulmo-cutaneum. 

 The synangium is the wide but very short part of the truncus which lies 

 in front of the three valves separating it from the pylangium. It is 

 completely divided by a horizontal partition, called the principal 

 septum, into a dorsal and a ventral chamber. The dorsal chamber 

 communicates with the cavum pulmo-cutaneum by an aperture situated 

 just above the middle and smallest of the three valves, and anteriorly 

 it is continued into the pulmo-cutaneous arteries. The ventral chamber 

 is divided by a vertical partition, called the septum medium, into two 



