The above list has been communicated by Dr. Bowerbank, F.R.S. It includes no less than sixteen species hitherto unpublished; but of which descriptions will appear in his work on British Sponges, now on the point of publication. It is chiefly in the Gouliot caves in Sark, that these sponges have been observed, but many of them are to be met with in all those accessible rocky bays and caverns that are covered during a large part of each tide. Some, as Grantia ensata, G. tessellata, tethea Collingsii, have never yet been found on British coasts; and as they are very remarkable, it is not likely they should have escaped the eye of British naturalists, had they really been present. The little sponge in the annexed cut is common enough on all the shores. Grantia compressa. Dr. Bowerbank observes, in a note he has been kind enough to add to his catalogue, that there are some interesting points in the characters of the marine species of the Channel Islands' fauna, from which it would seem that these shores and those of the south of Devonshire, are included in overlapping bands of the British and Mediterranean faunas. At Tenby and on parts of the Devonshire coast, are many species of sponges not found further north, but common in the Gouliot caves and elsewhere in these islands. Among them are pachymatisma Johnstonia, hymeniacidon caruncula, microciana atrasanguinea, isodictya rosea and halina Bucklandi. A similar overlapping takes place in a broad belt extending from about Scarborough to the Scottish Border on the east, and from the coast opposite Scarborough to the Hebrides, on the west. Here, also, there is a mixture of the spongiada that belong to the northern, with those of the southern seas, while on either side occur species that do not cross the line. These peculiarities are not, however, confined to the marine fauna.* The Gouliot caves, where the lower forms of animal life are so richly distributed, rival the celebrated caves of St. Catherine's Island, near Tenby, in abundance of specimens, and far surpass them in dimensions. It is impossible to visit the Gouliots without finding much that is interesting; but when the visit is made under favourable circumstances of tide, wind and weather, the phenomena are far more striking than can be understood from the most vivid and elaborate description. The Gouliots, however, are not the only spots where sponges can be observed. Along the south coast of Guernsey and also on the northern extremity of that island, in many parts of the Jersey coast, and on the shores both of Sark and Alderney, they may be found and examined with advantage, owing to the rough and irregular character of the rocks, the countless multitude of rock pools, and the extreme range of the tide. These causes have already been alluded to in speaking of the distribution of the zoophytes. The minute naturalist who pursues and discovers new beauties * Dr. Bowerbank is anxious to express his great obligation to Mrs. Collings, wife of the seigneur of Sark, to the late Mrs. Buckland, and to the Rev. A. M. Norman, of Sedgfield, Durham, who have assisted him with material, in addition to that obtained by himself during two visits to the Channel Islands, made for the purpose of observing and collecting the spongiada. in every nook and on every rocky prominence, will be amply rewarded in all the islands, and may with little difficulty enjoy the unusual satisfaction of watching, without interruption, the habits of the animals in their natural haunts. This is perhaps one of the chief attractions of the whole group, and it is limited to none of the islands. The mere collector will obtain a multitude of beautiful and rare specimens, and the discovery of the animals themselves, in their habitations, can hardly fail to excite a taste for the pursuit of the higher branches of natural-history study, and an investigation into the laws of existence of these simple animals. On the next page will be found a summary, in a tabular form, showing the details of the zoology of the Channel Islands. Little need be said here in explanation of the table, or in addition to the remarks already offered concerning each separate group of animals. That the Channel Islands are rich in most departments of animal as well as of vegetable life, that the island naturalists as well as strangers, have, with great labour and success investigated certain departments of the fauna as well as flora, and that the general interest of the district is unusually great, will be at once seen. That very much yet remains to be done in many important departments, is equally clear; and there is ample room for all in the investigations required. Whether on land; on a sandy or rocky shore above high-water mark, or in that wild and interesting field that intervenes between tides; or in those deeper recesses which the water never leaves;-life is ever present, and the forms of animal life are so rich, varied and beautiful, that no one need tire of the pursuit of natural history when placed within their range. The statements and lists given in this and the preceding chapter, will, it is hoped, be useful as marking a distinct position in naturalhistory knowledge, from which advance may be made in every direction. CHAPTER X. GEOLOGY AND MINERALOGY OF THE CHANNEL ISLANDS. ANCIENT FORMATIONS. IN no part of Europe, and in no group of islands readily accessible, are the physical geography and geology more closely related than in the Channel Islands. The tongues and spurs of porphyritic rock, of which almost all the promontories of the Atlantic coast of Europe consist, are well illustrated in Western Britany and in Cornwall, and not less so in the intervening rocky groups. Better able than most of the secondary rocks to resist the constant action of the sea, these rocks show themselves, partially denuded and generally rugged, in the neighbourhood of Cherbourg and Cape la Hague, but they appear in perfection in a succession of spurs pointing westward, forming the groups which together compose the islands we are considering. Exposed from their isolated position to the never ceasing beating of the waves during their elevation, these islands have been deprived of most of the covering of stratified rocks they may once have possessed, and except a patch here and there in the more sheltered positions, scarcely any indication exists of those deposited rocks that abound on all sides of them, and give variety to the geology of England and France. None of the |
