Our knowledge of the Antarctic fish-fauna has greatly increased during the last ten years. The Belgian expedition to Graham Land (1897–1899) was followed by that of the Southern Cross to Victoria Land (1898–1900), fitted out by Sir George Newnes. Next were the British expedition of the Discovery to Victoria Land and Edward Land (1901–1904), the German voyage of the Gauss to Kerguelen and Willhelm Land (1901–1903), and Nordenskjöld's Swedish expedition to South Georgia, the South Shetlands, and Graham Land. Then came the voyage of the Scotia to the South Orkneys and Coats Land (1902–1904), and Charcot's expeditions to the Palmer Archipelago and Graham Land in the Français. (1904–1905) and the Pourquoi Pas? (1908–1910), and finally Shackleton's expedition (1908–1909).

The first four parts of this work, on the skeleton, muscles, and vascular system, were published in the Transactions of the Society in 1905, 1907, 1909, and 1912.

The present section does not include the teeth, which, belonging properly to the skin, will be described when the skin and its appendages are dealt with. It will be noticed from time to time that I have to record striking differences from results obtained by other authors. Such differences must, of course, be recorded; but in recording them it must not be understood, unless the contrary is expressly stated, that the observations under discussion are necessarily inaccurate. One cannot investigate Myxinoid anatomy without frequently coming up against somewhat astonishing variations, and I have long been convinced that there must be races or colonies of Myxine which have not been distinguished specifically, but which, nevertheless, possess anatomical features in common. To give one instance out of many. Mr R. H. Burne has described in detail an anal slime gland in Myxine.

Although the osteology of Antarctic seals has been very completely discussed, notably by the late Dr J. E. Gray, Sir William Turner, and Professor Robert Thomson, yet the literature regarding the subject is somewhat scattered. I have therefore considered that it might be important from the point of view, as it were, of an index to publish a complete series of photographs of a set of the skulls of seals taken by the naturalists of the Scotia during the Antarctic voyage of 1902–1904.

For the opportunity of examining these specimens I am indebted to Dr W. S. Bruce, the leader of the Scottish National Antarctic Expedition, 1902–1904. I should like to take this opportunity of expressing my thanks to him, and also to Dr Marett Tims for his assistance during the preparation of the paper.

The Scottish specimens described in this memoir are all the property of Mrs Robert Gray, and I am exceedingly indebted to her, not only for entrusting them to me for description, but for allowing them to remain in my hands for a lengthy period. None of the collections of the Geological Survey, nor those of Glasgow University, contain any cystids from Girvan. Besides her Cystidea, Mrs Gray has submitted to me her Crinoidea and several interesting specimens of Edrioasteroidea.