ON THE SHETLAND CRUSTACEA, TUNICATA, ETC. 249 



have been found in the Moray Firth, but are wholly unknown on the eastern 

 coast of England. Moreover, many species have been recorded on the Nor- 

 wegian coast, though never found on the eastern shores of England, and 

 therefore may be presumed to have migrated thither up the western side of 

 Great Britain and round the north of Scotland ; as examples of such species 

 may be cited Pleurotoma striolata, attenuata, and septangular is, Cerithiopsis 

 tubercularis, Cerithium reticulatum and perversum, Rissoa violacea, Pliolas 

 dactylus, Solen vagina, Psammobia costulata, Gfastranafragilis, Isocardia cor, 

 Cardium aculeatum, Lepton squamosum, Xantho rivulosus, Portunus arcuatus, 

 Gebia deltura, &c. On the other hand, while northern forms do not extend 

 southward on the east coast beyond Yorkshire and the Dogger Bank, on the 

 western coasts they in many instances have a range southwards to the 

 Nymph Bank, off Cork, and even to the Mediterranean sea. Inasmuch, 

 therefore, as migration northwards has for the most part taken place by way 

 of the Hebrides and Shetland, a southern form which may be found in 

 the Gulf of Christiania or neighbouring part of Scandinavia, though at a point 

 of latitude considerably further to the south than Shetland, may be regarded 

 practically with respect to distribution to be further north, and a northern 

 species at Shetland as further south in its course of migration. In the pre- 

 paration, therefore, of the Tables IV. and VII. I have regarded the whole of 

 the Scandinavian sea as though it was to the north of Shetland, notwith- 

 standing that the latter is geographically situated in about the same latitude 

 as Bergen. 



As has been already stated, the chief aim of the Dredging Committee was 

 to thoroughly examine the invertebrata of the deep sea. This purpose was 

 never lost sight of, and the dredge was rarely let down in the Voes or other 

 shallow Avater except when we were driven there by stress of weather ; nor 

 was it possible to find much leisure, amid the constant labour entailed by the 

 examination and preparation of the animals procured by the dredge, to devote 

 to the littoral zone. Notwithstanding, therefore, the great length of the pre- 

 sent catalogue (which shows the fauna in almost every branch to be more 

 rich than that of any other portion of the British coast which has been care- 

 fully examined by competent naturalists) there cannot be a question that 

 numerous and interesting discoveries will reward the future investigations of 

 zoologists near the shore as well as in the open sea. For with regard to the 

 latter, our repeated dredgings in these northern waters have only sent us 

 home each time more fully convinced how much remains to be done before 

 we can attain anything like a complete knowledge of the animals which 

 inhabit them. "We never tried a new locality a few miles distant from that 

 which we were before examining that we did not meet with species which 

 had been previously unnoticed : in fact the Shetland seas appear to afford an 

 inexhaustible treasury of rare animals in every department of zoology. 



While some species are extremely widely diffused, though numerically 

 scarce, throughout the province, others are common everywhere, and others 

 again apparently excessively limited in their distribution as well as very rare 

 when found. But one of the most remarkable features in the distribution of 

 life in the Shetland Sea is the extraordinarily circumscribed habitat, but at 

 the same time the local profusion, of many species. It will not be without 

 interest to give a few examples of this. Many Crustacea, as Nilca edulis, 

 Dorypliorus Gordoni, Uastrosaccus sanctus, &c., occurred on one occasion in 

 one spot in considerable numbers, but were scarcely ever (if ever) seen again. 

 Forty miles east of the Whalsey Skerries Echinus Norverjicus was in such 

 extraordinary profusion that the dredge came up again and again literally 

 almost filled with it ; but though occurring in many other localities, it was, 



1868. T 



