On new Species of Stromatopora. 89 



three branchial arches of the mackerel, however, bear no long 

 teeth, but an outer and inner series of tubercles with spines. 

 By means of this latticework of teeth and spines the mackerel, 

 like the herring, can easily filter great masses of Copepods 

 from the water. According to A. Boeckh (Forhandl. Vid. 

 Selsk. Christ. 1864, p. 227), the autumn mackerel on the 

 Norwegian coast become fattened by abundant Copepod 

 nourishment. On the east coast of Schleswig and Holstein 

 the mackerel appears in considerable quantities only from the 

 beginning of July to the end of September ; from autumn to 

 spring therefore, when the shoals of sprats and herrings 

 appear here, the mackerel does not deprive them of any of 

 their best food. 



Where multitudes of food-animals occur, there also, as a 

 general rule, multitudes of fishes collect. The herrings pursue 

 the Copepods ; and the cod ( Gadus morrh.ua) follow the herrings. 

 For a long time there had not been so many large cod taken 

 between the fortress of Friedrichsort and the village of Labo as 

 in the winter of 1871-72, when the herrings were so plentiful. 



For carrying on the fishery, such a gathering together of 

 great shoals of fishes belonging to the same species is of great 

 value. Social animals of the same kind lead a similar life. 

 They seek their food in common, become sexually mature at 

 the same time, and collect, for the purpose of spawning, at 

 definite spots. Thus the fisherman finds them at certain times 

 in great numbers together, and can reckon beforehand on 

 making a good haul with properly designed instruments of 

 capture. But where many different species live, the fisherman 

 cannot take an equal weight of fish with the same amount of 

 labour, even when the sum of all the individuals in the same 

 space is as great as the number of individuals of a single species, 

 because each different species has a different nature, and con- 

 sequently must be circumvented in a different manner. Hence, 

 whilst the rich southern fish-fauna breaks up the work of the 

 fishing-population and renders it less remunerative, the 

 northern fish-fauna, which, although poorer in species, is rich 

 in individuals, leads to a powerful and remunerative concen- 

 tration of the business of fishery. 



XI. — On some new Species of Stromatopora. By H. Alleyne 

 Nicholson, M.D., D.Sc., F.R.S.E., &c, Professor of 

 Natural History in University College, Toronto. 



[Plate IV.] 



The affinities of the singular genus Stromatopora have always 

 been more or less uncertain, though there has been a general 



