100 
PROFESSORS T. W. BRIDGE AND A. C. HADDON 
neural canal between the claustrum and the ascending process of the scaphium in 
Silurus giants. On this point we can only say that after a most careful examination 
we have utterly failed to satisfy ourselves that any such nerve exists in Macrones. 
Ramsay Wright (44) states that he has been equally unsuccessful in detecting this 
nerve in Amiurus catus. 
Other Species of Macrones. 
Of the lemaining species of Macrones recorded in the ‘ British Museum Catalogue/ 
we have examined the following : — M. planiceps, M. nigriceps, M. gulio, M. tengara, 
M. Woljfii, M. micracanthus, M. Hoevenii, and M. aor. We also dissected a species 
labelled AI. armatusf but which we were unable to identify with certainty as belonging 
to any of the species referred to in the ‘ British Museum Catalogue/ or elsewhere. 
With the exception of the last-mentioned, the locality of which was unknown, all 
these species are East Indian, collectively ranging from India eastwards through 
Burmah, Siam, Java, Sumatra, and Borneo. 
With the exception of Alacrones aor the variations met with in the structure ot 
the air-bladder are perhaps of no great importance, but nevertheless merit a brief 
reference from the fact that they illustrate the nature and extent of the modifications 
that may occur in the normal sjiecies of the same genus, and Macrones is one of the 
very few genera of which we have been able to examine a fairly representative series 
of species. 
AI. planiceps and AI. armatus very closely resemble Al. nemurus. The same remark 
applies also to AI. nigriceps, AI. gulio, AI. tengara, and Al. Woljffii, except that the 
lateral compartments of the air-bladder in these species have comparatively undivided 
cavities, there being but slight rudiments of two or three secondary transverse septa 
in each. The po.st-temporal plates may also vary slightly in the depth of their 
posterior concavities. In AI. micracanthus all traces of secondary transverse septa 
have entirely disappeared. In AI. tengara the lateral cutaneous areas are rendered 
very evident externally by circular patches of black pigment, and, as Gunther (15) 
remarks, these ocellus-like patches are more conspicuous in young than in old speci- 
mens. In AI. Wolfii the walls of the bladder are somewhat thicker than in any other 
species of Macrones, and the lateral compartments relatively smaller. In M. Hoevenii 
the post-temporal plates are unusually expanded, and form rounded or somewhat oval 
laminae of bone, thin, brittle, and cancellous at their edges, but much thickened 
towards the centre of their anterior faces, where each is perforated by a tubular 
socket for the head of the clavicle. The posterior face of each plate is much more 
concave than is the case with any of the preceding species, and, as in Al. nemurus, 
the concavity is still further deepened round its inner and ventral margins by the 
unusually long and slender crescentic portion of the transverse process of the fourth 
* This specimen was given to us by Dr. Day. 
