I2O ALLEN 



second and third branchial levator muscles ; the anterior branch 

 continuing on across the outer surface of the second branchial 

 levator muscle, unites with the first branch mesad of the first 

 levator muscles ; while the posterior branch passes mesad 

 between the second and third branchial levator muscles to ter- 

 minate in the anterior ventral corner of the posterior part of the 

 branchial sinus through an orifice designated in Figs, n and 12 

 as D.Br.L.T.(2)O. The third branchial trunk after leaving 

 its arch curves around the fourth levator muscle to culminate in 

 the floor of the posterior division of the branchial sinus about 

 opposite the fourth branchial levator muscle (Figs, n and 12, 

 D.Br.L. T.(3)O.); whereas the trunk from the fourth arch dis- 

 charges itself in an entirely different sinus. Its opening (Figs. 

 8, 9, ii and 12, Br.L.T.(^)O.) is through the inner wall of 

 that part of the occipital sinus which lies mesad of the peri- 

 cardial sinus. 



All of the so-called ventral branchial trunks doubtless termi- 

 nate in one way or another in the inferior jugular vein. This is 

 certainly true for the first three pairs, but the final ending of 

 the last pair I have never been able satisfactorily to trace out. 

 Each of these ventral branchial trunks has its source from the 

 ventral filaments, and traverses between the two hemibranchs, 

 in company with, but distad of, the afferent branchial artery. 

 The first pair of these vessels discharged themselves through 

 two orifices (Figs. 14 and 15, V.r.L.T.(i)O.) situated in the 

 dorsal walls of the right and left forks of the inferior jugular, 

 directly in front of their corresponding afferent branchial arteries. 

 In the specimen from which Figs. 14 and 15 were drawn, the 

 second right branchial trunk joined the right fork of the inferior 

 jugular exactly in front of the second right afferent branchial 

 artery through an orifice designated as V.r.L.T.(2)O. The 

 precise point of union of the third right trunk was not located, 

 but upon injecting this vessel ventrad with water it was dis- 

 charged through the opening of the right fork of the inferior 

 jugular into the inferior jugular (Fig. 15, R.I.J. V.O.} 9 indi- 

 cating of course that it came from the inferior jugular. In 

 the dorsal wall of the left fork of the inferior jugular, imme- 

 diately behind the second left afferent branchial artery, there is 



