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Show 1894.] ON THE VISCERAL ANATOMY OF ORNITHORHYNCHUS. 715 There is no separate inferior mesenteric artery, in this respect agreeing with certain Marsupials. Arteries of Head and Neck. The common carotid.-Is a large artery arising from arch of aorta on left side, from innominate on the right. It divides at about the level of the thyroid cartilage into external and internal carotid. Just at the point of bifurcation an artery is given off Avhich passes directly inwards and divides in a regular cross-like manner into ascending, transverse, and descending. The ascending and descending pass to the pre-vertebral muscles ; the transverse to the back of the larynx and trachea. The external carotid.-Passes upwards and backwards; gives off a branch to the supra-hyoid and genio-hyoid muscles. More anteriorly a small lingual artery arises. There is a second smaller lingual just above this, next to submental branch which runs along the whole length of the inferior surface of the lower jaw, close to the bone. Coming off here, in addition, are two slender branches, one passing to the sub-lingual gland, the other to superficial structure, skin, &c. A little higher arises an artery which divides almost immediately into tAvo branches, one passing to the inner surface of the loAver jaw, the other to the outer surface; they may represent internal and external pterygoid arteries. The internal is fairly large and gives off several branches to the cheek-pouch. The trunk artery passing a little further on divides into two branches; one, passing to the superficial structures on the side and roof of the skull, is distributed to the deep structures in these regions. Internal carotid.-Passes deeply at the neck and divides into two branches. The smaller passes deeply beneath pharynx and in front of the longus colli muscle to the anterior margin of foramen magnum. The other is the continuation of the trunk, passes upwards and enters the skull. 2. O n some Points in the Visceral Anatomy of Ornithorhynchus. By F R A N K E. B E D D A R D , M.A., F.R.S., Prosector to the Society. [Eeceived December 4, 1894.] Mr. B. P. Lascelles, assistant master at Harrow School, was so good as to allow m e to examine a frozen Ornithorhynchus which he had obtained for the purpose of making a skeleton for the Butler Museum at Harrow. After thawing, I found the viscera in a very fair condition for anatomical investigation, though they were naturally somewhat softened. The first point to which I directed m y attention was the |