39 



on to the arches, the only connection between the arches 

 and the rakers being" that in older specimens and in some 

 places the position of the raker is indicated on the arch by 

 a faint elevation. Their nnniber and position, however, 

 was in the few specimens examined remarkably constant 

 and symmetrical, so that the following formula may apply 

 to either side of most individuals : — 



H}po-branchial 

 Cerato-branchial 

 E pi- branchial 



V. 



Gill Rays. — The gill filaments are supported by series 

 of very delicate fragile gill rays fused together by their 

 bases like a comb, which it is hardly practicable to dissect, 

 but which are quite obvious in sections of the gills. They 

 radiate out from the branchial arches as usual, and occur 

 in pairs — one to each demibranch of the arch. 



Eyeless Side. 



Branchial Arch I- — -All segments slightly shorter and 

 not so robust, the hypo-branchial markedly so, nor is the 

 latter so deeply socketed into basi-branchials I. and II. as 

 on the ocular side. The pharyngo-branchial also articu- 

 lates with the skull, but the depression in the skull with 

 which it is connected is deeper and more marked. 



Branchial Archil. — Practically no difference except 

 that the basi-branchial articulation is stronger on the 

 ocular side. 



Branchial Arch III. — The segments are of the same 

 length, but are somewhat less robust. The ventral arch 

 transmitting the ventral aorta has been already described. 



