Brain and Cranial Nerves of Acanthias vulgaris. 183 
XIV.—The Brain and Cranial Nerves of Acanthias vulgaris, Risso; 
with some remarks on those of Galeorhinus galeus (Linn.), 
-and of Pristiurus melanostomus, Giinther. By G. L. Purser, 
M.A.(Cantab. ). 
(With Six Plates and Text-figure.) 
(Read 27th January 1919. MS. received 28th December 1918.) 
THE following is mainly a description of the brain and cranial nerves of 
Acanthias, in explanation of the drawings made from dissections. 
The work, of which these figures are the outcome, was undertaken 
because at the present time a large body of students studying elementary 
zoology in this country use this species instead of Scylliwm, and it was 
thought, therefore, that careful figures which include at least as much detail 
as is usually demonstrated to such students, should be published. 
While doing the work on Acanthias, I took the opportunity given me by 
Mr Renouf of dissecting the nervous system in one specimen of Galeorhinus 
and in a few of Pristiwrus, and so, although I shall not give a full account of, 
but only describe the chief points of interest in, their structure, I am 
publishing the drawings made of them. 
My thanks are due to Professor J. Graham Kerr for his valuable sugges- 
tions with regard to the method of illustration to be used, and for his kindly 
criticism of the manuscript; andl, finally, I must acknowledge my indebted- 
ness to Mr L. P. W. Renouf, the Director, for giving me every facility for 
work at the Bute Laboratory and Museum, Rothesay, from which the 
material was obtained, and at which most of the dissection was carried out. 
IL.—TuHE BRAIN AND CRANIAL NERVES OF AGCANTHIAS. 
The Rhombencephalon (Figs. 2, 4 and 5)—The Medulla Oblongata 
appears, as in all other forms, as an anterior expansion of the spinal cord, 
so, as far as can be seen with the naked eye, there is no line of demarcation 
between them. The expansion, which is rather more gradual than in 
Scyllwwm and so forms a longer Medulla, is due to the enlargement of the 
central canal as well as to the thickening of the lateral and ventral walls. 
The cavity is here known as the [Vth ventricle of the brain, and its dorsal 
wall, with the exception of the most anterior and posterior portions, is thin, 
non-nervous in character, and highly vascular. The thin portion of this 
dorsal wall, with its choroid plexus, was removed from the brains from which 
the drawings were made. 
