1910.] ANATOMY OP THE FRILLED SHARK. 549 



one side and two on the other, lying close to the ceratobranchial 

 of the sixth arch on the posterior side near to the median 

 extremity. 



e. Branchial Rays. 



These are thin, tapering rods of cartilage lying embedded in 

 the interbranchial septa, a, little closer to the inner surfaces of the 

 latter than to the outer. Proximally they are applied to the 

 posterior sides of the branchial arches, and distally they project 

 somewhat beyond the margins of the interbranchial septa, to 

 which they thus give a crenulate appearance. 



One or two cases were observed in which two rays appeared to 

 be fused pi-oximally, appai-ently having a common origin. In 

 another case two rays which had separate origins fused, and 

 became produced so as to form one ray. 



The greatest number of rays occurs on the hyoid arch, and as 

 we proceed posteriorly the number gradually decreases for the six 

 branchial arches, though subject to some variation. The sixth 

 arch carries no distinct rod-like rays, but a thin laminate portion 

 (l.p.) is found on the anterior ventral edge of the ceratobranchial. 

 This, as previously mentioned, is regarded by Fiirbringer as the 

 representative of the branchial rays fused with the ceratobranchial. 

 Whether this is the case or not, appears to me to be an open 

 question. This lamina may be merely a thin extension of the 

 ceratobranchial. Again, there seems to be no particular reason 

 why the original branchial rays — if such were present — should 

 have fused into a common lamina and have become firmly 

 attached to the arch. As a rule, it appears, branchial rays are 

 not met with on the last arch in Selachians, and why this portion 

 should be looked upon as their representative in GUamydoselachxis 

 it is somewhat difficult to understand. The first series of numbers 

 in the following tables is from the complete male specimen ; the 

 second is from the large female. Both right and left sides are 

 given. 



Male. R. L. 



Hyoid arch 28 26 



First branchial arch 18 17 



Second ,, ,, ...... ........ 16 17 



Third „ „ .................. 14 14 



Fourth „ „ 13 14 



Fifth „ „ 10 9 



Female. 



Hyoid arch 25 27 



First branchial arch 19 19 



Second „ ,, ...... .... 14 16 



Third „ „ 15 14 



Fourth „ „ 14 12 



Fifth 9 L0 



