880 Mft. WALTER E. COLLTITGE OIT THE SETfSORt [DeC. 17, 



branch divides into maxillary and mandibular divisions ; anteriorly 

 the former division meets with the sub-orbital branch, previou? to 

 which, however, it gives off a vertral flexure. No short or 

 dendritic branches are given ofE from either the lateral or main 

 canals or the larger branches. There is also an absence of primi- 

 tive pores, and the cluster-pores are very few in number. In 

 certain parts of the canals of the head there are large diamond- 

 shaped openings. In these regions the canal is distinctly larger 

 and is supported and protected by a series of cartilages. 



2. Course of the Canals and Branches. 



1. The Lateral Canal commences a few millimetres from the 

 end of the long whip-like prolongation of the tail. Its course lies 

 on the lower side of the muscles of the trunk. Eising slightly 

 dorsally, it passes on to the sides of the body and continues for- 

 wards as an open groove to the region of the head. There are no 

 branches of any description passing off from the lateral canal, a 

 feature so characteristic of many Elasmobranchs. 



2. The Main Canal of the Head passes directly dorsally, 

 giving off an occipital commissui-e, and then passing forwards and 

 shghtly inwards. Where the main and lateral canals meet with 

 the sub-orbital branch, in some of the specimens examined a small 

 forvvardly directed branch was given off (PI. LI. fig. 2, x.). 



The Supra-orhital Branch commences where the main canal of 

 the head turns as a forward and slightly outward branch. It 

 passes above the orbit to the tip of the snout, and then makes a 

 sharp turn and meets «iththe sub-orbital branch (PI. LI. fig. l,Sp.o.). 



The Sub-orbital Branch leaves the main canal of the head at its 

 commencement and passes ventrally, giving off a short jugular 

 branch, and immediately in front of this the maxillo-raandibular 

 branch. The sub-orbital branch continues forwards making a 

 somewhat S-shaped cm-ve and meets with the supra-oi-bital branch. 

 At the point where these two branches become connected thez'c is a 

 Y-shaped commissure connecting the supra- and sub-orbital branches 

 of either side of the head with the maxillary division of the 

 maxillo-mandibular branch (PL LI. fig. 1, S.or.). 



The Maxillo-mandibular Branch is given off from the sub-orbital 

 branch. The maxillary division passes above the upper jaw, 

 meeting with its fellow of the opposite side. It also gives off 

 dorsal to this, on either side, a short branch which meets with the 

 base of the Y-shaped commissure previously described (PI. LI. 

 fig. 1, Mx. & Mn.). 



The mandibular and jugular branches are evidently subject to 

 much variation. In most of the specimens I have examined the 

 former do not meet at the symphysis, but terminate at either side 

 of the mouth ; in others there is an interrupted canal, as figured 

 by Q-arman (9. pi. ii. fig. 5). The jugular bi-anch this author 

 figures as passing backwards to the region of the pectoral fin, 

 where it makes a sharp inward curve and runs as an interrupted 



