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& Note on the Extra-branchial Cartilages of Seyllium canieula. 
By Pamir J. Waite, M.B, F.R. 8. E., Professor of Zoology, University 
College of North Wales, Bangor. 
The latest description of the extra-branchial cartilages of Scyl- 
lium canicula is as follows: — “The extra-branchials are three pairs 
of elongated curved rods lying along the outer sides of, and beneath 
the second, third and fourth branchial arches” !). It is not clear from 
this description that the cartilages belong to and are in connection 
with the first, second and third branchial arches. But this is a minor 
point. Why, however, is no mention made of the upper extra-bran- 
chials? There are four of these cartilages on each side. They com- 
mence at the upper and outer part of the anterior cardinal sinus, and 
extend outwards and backwards along the upper edges of the gill 
plates of the first, second, third and fourth branchial arches. The 
cartilages, as is usual among Selachians, are shorter and slighter than 
the lower extra-branchials. I have found no separate extra-branchial 
belonging to the hyoid arch, but it may be noted that one or two of 
the upper hyoid gill rays send upwards a slender bar which lies in 
the position which the extra-branchial of the hyoid occupies when it 
is present. 
Thus there are four pairs of upper and three pairs of lower extra- 
branchials. They are associated with the first, second, third and fourth 
branchial arches, but in the case of the fourth arch the lower extra- 
. branchials are absent. The upper extra-branchials in Scyllium would 
call for no comment were it not that they appear hitherto to have 
escaped notice in an animal which has received much attention from 
morphologists and students. It is difficult to understand how they 
should have been overlooked. 
1) Practical Zoology, Marsuatt and Hurst, 4. Edit., p. 228, 1895. 
