ERRATA 



wide right and left passages. The left passage leads into the systemic 

 aorta of that side. The right passage is open behind to the cavum 

 aorticum, and anteriorly it is continued into the carotid arteries and 

 the right systemic aorta. " 



P. 48, 1. 38. For " upper " read " ventral." 



P. 48, 1. 39. For " lower" read "dorsal." 



P. 57? ! ^6. For " synangium " read " cavum pulmo-cutaneum. " 



P. 57, last line. Delete from "it seems" to "carotids," 1. 5, p. 59. 



