12 THE FISHERIES OF THE ADRIATIC, 



also Arenicola branckialis, a species of lug-worm, which, together with the 

 Nereis, are caught by fishermen for bait. 



ZONE III. — The Submerged Littoral Zone, extending from low- 

 water mark to a depth of 2 fathoms; average temperature of water 59 F., 

 subject to rapid changes ; characterised by forty species of Mollusks, ten 

 Crustacea, six Annellides, four Echinoderms, four Polyps, three Amorphozoa. 



This is the region of the corallines, more especially of the pretty calci- 

 ferous sea-plant Corallina officinalis, which marks its appearance just below 

 low-water mark ; these are often overgrown by dense Cystoseira, forming the 

 most prevalent and striking facies of this region. Another prevalent facies is 

 that of the waving meadows of Zostera, or grass-wrack, which grows on sand 

 or mud. This mass of vegetation is interwoven by Diatomaceae, of which fifty- 

 nine species, belonging to twenty-six genera, belong exclusively to this region. 

 At a depth of 4 to 10 feet commence the Nullipores, coral-like vegetables, 

 simulating minerals in figure and consistence, and furnishing a favourable 

 spawning-ground for fishes ; they grow in vast quantities, and assume many 

 strange modifications of form, sometimes expanding into small cabbage-heads, 

 but mostly assuming the appearance of coral. Nullipore ground is very 

 necessary to the development of animal life, as it harbours a number of forms 

 which are scattered by its destruction ; hence the value attached to its 

 preservation. On rocky shores are found several species of the Polyp 

 Actinia, chiefly A. viridis ; more rarely A. aurantiaca, A. rlwdodactylos, 

 A. bimacnlata: Echinus lividus adheres to the rocks, Bonellia viridis lies 

 in crevices ; Purpura maculosa, Trochus fragarioidcs, T. tessellatus, Patella 

 ccerulea, Chiton siculus, Spondylus aculeatus just below the surface on Algae, 

 as also the crustaceans Grapsus varius and Palccmon squilla. 



On corallines are found Conus mediterraneus, Murex cristatus, and different 

 species of Trochus (T. Laugieri), all shells of varying beauty. Here and 

 there appears the Echinoderm Asteracanthion glacialis, common to the Boreal 

 and Celtic regions, sometimes as much as 7 to 8 inches long, often left dry by 

 the receding tide and anxiously clinging to the rocks. Asteracanthion 

 tcnuispinus is found less frequently. 



