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Show 280 ME. W. E. COLLINGE ON THE [Apr. 2, which opens by a pore over the region of the supra-clavicle (McMurrich) (PI. XVIII. fig. 2, x). 2. T H E M A I N C A N A L commences from the point where the above-mentioned branch leaves the lateral canal. It passes through the frontal opening by a pore, immediately in front of which the occipital commissure is given off; some little distance in front of this the main canal receives the operculo-mandibular branch. Its course is now directed forwards and inwards, two pores opening in front of the operculo-mandibular branch. At some little distance posterior to the orbit the canal divides info the supra- and sub-orbital branches. The Supra-orbital Branch.-At the point of division a backwardly directed branch is given off, which passes towards the mid-dorsal line (PI. XVIII. fig. 2) opening by pore number 12. The supra-orbital branch continues forwards above the orb't, giving off another branch, which also passes backwards and almost parallel to the main branch ; a little distance in front of this a pore opens to the surface, and the canal enters a small canal-bone, through which its passes, giving off a lateral branch which meets with the sub-orbital branch, thus establishing a connection between the two in front of the orbit. After leaving this bone it makes a lateral curve and terminates blindly at the side of the maxillary barblet. The Sub-orbital Branch is formed by the lower division of the main canal. It passes forwards and outwards for a short distance, and then makes a curve be math the orbit, passing through tbe infra-orbital series of canal-bones, and in the anterior region enters a small canal-bone-the antorbital of some authors; passing through this it opens on the inner side and communicates with the supra-orbital branch. The Operculo-mandibular Branch.-I have already stated that this branch is connected with the main canal; this connection is established by four email drainpipe-like canal-bones which pass from the region of the posterior border of the hyomandibular bone to the lateral border of the frontal (PI. XVIII. fig. 3, cb.). Passing from the main canal into this series of canal-bones, and through the external portion of the hyomandibular bone, the canal enters the preoperculum; from here it passes into the distal portion of the quadrate and then into the mandible, opening by four pores in its course. 3. T H E C O M M I S S U E E S . - T h e only commissure present is the occipital commissure, which connects the main canal of the head of either side with each other. There are two pores opening from it, being situated one on either side of the rredian line. There is no commissure in the anterior or frontal region. Innervation. The cranial nerves of Amiurus catus have been described by Ramsay Wright (13), and I have little or nothing to add to his account, excepting their relations to the sensory canal system 2 f The absence of careful figures makes this otherwise excellent account very ctimcult to follow, the figures on plates i. & iv, being xerj diagrammatic, |