240 - Proceedings of the Royal Physical Society. 7 a 
If a record were kept of the occurrence or non-occurrence Ol 
variations in dog-fishes, by those who see large numbers of them < 
for teaching purposes, an interesting and suggestive comparison n 
made as to the variability of, and the direction of variation in the < 
system of the two groups of Elasmobranch fishes. Bae 
The specimens described are preserved in the museum of the Natur 
History Department, Edinburgh University. | | | 
EXPLANATION OF FIGURES. 
All the figures:are x? and represent ventral dissections of the heart and afferent 
branchial system. 
* 
S.V. Sinus venosus. 0. Conus arteriosus, P.I. Posterior innominate. 
A, Auricle. V.A. Ventral aorta. G. Gill clefts, , oo a 
We Ventricle, A.J, Anterior innominate, 1-5 Afferent branchial arteries, an 
(Issued separately, 6th June 1921.) 
