ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 369 



dorsal and anal fins, whose fin-rays are supported by interspinous bones 

 ■alternating with the neural and haemal spines. There is a space devoid^ 

 of fin-rays (six or seven vertebrae) separating the caudal fin from the 

 last vertebra with fin-rays attached. Two large hypural bones are 

 present, fused at their bases, and firmly fixed or fused to the last 

 centrum. Tlius the caudal fin is ivholly a ventral structure in this fish, 

 whereas in the majority of Teleosts a few dorsal elements enter into the 

 caudal fin. It is probable that the caudal fin in Ghaudlmrki is a more 

 definite propulsive organ than in other Apodes. J. A. T. 



c. Greneral. 



Fauna of Coastal Waters. — C. G. Joh. Petersen {Rep. Danish 

 Biol. Stat., 1918, 25, 1-62, 11 pis., 16 figs.). A survey is taken of the 

 work done from 1883-1917 in the valuation of the sea-bottom in 

 Danish coastal waters. Much information has been obtained by 

 using, in addition to the dredge, etc., various forms of " bottom- 

 sampler." The sea-floor near the coasts shows flat plains of sand, mud, 

 or clay, or transition stages between these, with or without stones. The 

 vegetation consists of Zostera and Algge. It is not as a rule consumed 

 living, but is spread about in the form of detritus and then eaten. It 

 forms a thin layer on the mud, and is far more important than the 

 microscopic plankton. Eight distinctive animal communities are dis- 

 tinguished, and these are named after characteristic types : — Maconia, 

 Air a, Venus, Echinocardium cor datum and Ampklura fiUformis (con- 

 tracted to Echinocardiuni-filiformls), Brissopsis tyrifera and Amphiura 

 chiajei (contracted to Brassopsis-chiajei), Brissopsis lyrifera and Ophio- 

 glypha sarsii (contracted to Brissopsis-sarsii), Arnphilepis-Fecten, and 

 Baploops. Wherever there are stones, waving plants, or the like, of 

 considerable size, there is an " epifauna," such as the llodiola-einf amm 

 or the 3Iytiliis-eTg[famm. The nature of the epifauna communities or 

 of the level-living communities depends on the nature of the bottom, 

 the temperature, the salinity, the depth, the storms, or the inter- 

 relations established. In the Kattegat there are towards 24 millions of 

 tons of plants (about 4 millions of dry matter), about .5 millions of tons 

 of " useless " animals, about 1 million " useful " forms — namely, those 

 which furnish or may furnish food for fishes. It is estimated that there 

 are only some few thousands of tons (5-7000) of each important 

 species of food -fish, such as plaice, cod, and herring. Starfish make up 

 25,000 tons — more than all the important food-fishes altogether — while 

 predatory Crustaceans and Gastropods amount to no less than 50,000 

 tons. The food-fishes, being predatory animals, are far from economical 

 to produce. Only a relatively small number can be supported in a given 

 area — and it has to be borne in mind that some animals are much more 

 nutritionally valuable than others. Much of the weight of the animals 

 consumed by fishes may be lime-salts or water. A detailed investigation 

 of a limited area (Limf jord) shows that the quantity of fish-food avail- 

 able is by no means unlimited. Indeed, ithere may be more fish^ — ■ 

 — e.g. plaice — per acre than the water can stand if they are to grow 



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