500 
that the account in the former textbook is largely *), and that in 
the latter wholly based on PArker’s classical work on the “Structure 
and Development of the Skull in Sharks and Skates” *), and that it 
is not unnatural that any errors which have unfortunately crept into 
this work should have found their way into the above-mentioned 
textbooks. 
WHITE, referring to the upper extrabranchials of Scyllium 
canicula, writes that they “would call for no comment were it 
not that they appear hitherto to have escaped notice”, and that “it 
is difficult to understand how they should have been overlooked”. 
As a matter of fact, their existence, well known to teachers of com- 
parative anatomy, was recorded in this species as long ago as 1832 
by RatuKe®) (p. 83) in his excellent treatise on the branchial ap- 
paratus of vertebrates®), a work which Waite has evidently not 
consulted, or he would have seen that, although in MARSHALL and 
Hurst’s textbook the three lower extrabranchials are stated to occur 
on the second, third and fourth branchial arches, they. had previously 
been correctly located on the first, second and third. 
The presence of the five superior and five inferior extrabranchials 
in Acanthias vulgaris (Squalus acanthias), which Foote 
claims to have discovered, was also observed by RATHKE; and the 
extrabranchials of the skates, for the discovery of which Foore 
takes credit to himself, have been recorded by RATHKE in Raia 
aquila, and by GEGENBAUR?) in Rhynchobatus and Trygon. 
Foore continues to the effect that “none of the morphologists who 
mention the extrabranchials offer any explanation of them”. This is 
a most astounding statement in view of the well-known theories of 
RATHKE*), Cuvrer®) and Donrn’®). I would especially commend 
to the notice of this author Donrn’s fifteen page account of the extra- 
branchials of Elasmobranchs, with its carefully sought out excerpts 
from RATHKE, CUVIER, JOHANNES MÜLLER !°), GEGENBAUR and 
3) Anat. Anzeiger, Bd. 11, 1895, p. 428. 
4) Trans. Zool. Soc., Vol. 10, 1879. 
5) Untersuch. über den Kiemenapparat und das Zungenbein der Wirbel- 
tiere, Riga und Dorpat 1832. 
6) Ratuxe, however, failed to detect the upper extrabranchial on the 
fourth branchial arch. 
7) Kopfskelet der Selachier, Leipzig 1872. 
8) Lecons d’ anat. comp., ed. 2., Tome 7, Paris 1840. 
9) Mitt. Zool. Stat. Neapel, Bd. 5, Leipzig 1884. 
10) Vergl. Anat. der Myxinoiden. 
