190 Proceedings of the Royal Physical Society. 
transverse groove becomes very apparent when the half-brain is examined 
(Fig. 15). 
Galeorhinus possesses the most complex Cerebellum of any known fish, 
Amphibian or Reptile (Figs. 7,9, and 10). It is rather prismatic in shape; 
tall with a longitudinal ridge, from which it gradually widens to its base. 
Its surface shows four unpaired transverse sulci and a pair of lateral ones 
between the second and third unpaired ones. There are no longitudinal — 
grooves at all. The anterior sulcus is very long, and on nearing the base 
turns round and runs up parallel to its first part about half-way back towards 
the apex. In median sagittal section, internal folding of the walls of the 
sulci already mentioned increase the complication already found, while 
two other sulci at the posterior end which are hidden by the Restiform 
Bodies add to it still more. The wall, as compared with that of Acanthias or 
WI oph 
", Y- obh 
| 
braig 
Brain of Scylliwm, seen from side. Nat. size. 
Scylliwm, is thin and shows that the sulci are produced by true folding rather 
than by the splitting up of a solid mass of tissue. 
The careful dissection of the Medulla in these species has made me very 
doubtful as to the accuracy of the figures generally given for the brain of 
Scylliwm with regard to the roots of the cranial nerves. What I have termed 
the VIIIth, VIIth, and Vth complex is in all the three species, with which 
we are concerned, on the same plan, and, except for the VIIIth, it is impos- 
sible to treat the branches, still less the trunks, as individuals or to identify 
their individual roots. The dissection of this region is very difficult, because 
the nerves are embedded in a compact mass of cartilage and because their 
sheathes, their toughest parts, are continuous with the perichondrium. 
Nevertheless, I am confident that my figures are true representations of the 
roots and of the trunks arising from them, and that the labelling is correct 
as far as it goes. Where I am not absolutely confident, as in Prostiurus, 
I have omitted detailed labelling, and have only put comprehensive names 
to the parts. So there has been neither straining of names to fit accurate 
drawing nor touching up of drawings to agree with names. 
” ——- = eo” 6h 
