252 



REPORT 1868. 



with. great care. In the second column many species are omitted which, 

 though contained in the first, are not considered by me to he distinct from 

 other described species ; consequently the difference between the number 

 of British species now known, and those which had been recognized previ- 

 ously to 1861, is even greater than appears from a comparison of the figures 

 here inserted. 



3. The number of species which have heen found in the Shetland seas. 

 The inland forms are entirely omitted from these columns. The small area of 

 the Shetland Islands, their isolation, the stunted character of the vegetation, 

 the almost total absence of trees, and the scarcity of ponds or pieces of 

 water other than moorland tarns (which character of water has a restricted 

 fauna peculiarly its own), all tend to limit the numbers of land and fresh- 

 water invertebrata likely to be found in the islands. Our object was the 

 investigation of the marine fauna, and but little attention was paid to that 

 of the land. Those few species, however, which were observed will be found 

 enumerated in the Catalogue, and consist of twenty-two Crustacea (out of 

 one hundred and fifteen known as British) and one Hydrozoon. 



