20 THE FISHERIES OF THE ADRIATIC, 



of the Ascidians Phallusia cristata, and more especially P. mammillata 

 entwined with Dictyomenice, are most characteristic. Quantities of Tzirritella 

 communis and Aporrhais pes pelicani here first make their appearance, 

 whilst the bivalves Corbula nucleus and Pecten inflexus seem to be limited 

 to this region, and form one of its principal facies. The Capanus, or 

 Dry-rot-worm, Teredo navalis, the " calamitas navium," or the scourge of 

 vessels, as it has been called, is found in sunken pieces of wood, and is 

 especially prevalent at Sebenico. Lastly may be noticed the Annellides 

 Aphrodite hystrix, A. sericea, the Crustacean Portunus plicatus and species 

 of Ophiolepis. 



Some species descend here from the former region, such as Lambrus 

 angulifrons, Portunus Rondeletii, &c. ; the Echinoderms Asteracanthion 

 glacial is, Astropecten aurantiacus, A. platyacanthus, and Echinus microtuber- 

 culatus. But they disappear entirely in the course of this zone ; Astropecten 

 aurantiacus is at its height of development here. 



Last of all may be mentioned on loam-beds the sponge Esperia massa, 

 and other yellow and red sponges ; also the Echinoderms Echinaster sepositus, 

 Ophioderma longicatida, Astropecten pentacantlms, and Cucumaria pentactes : 

 the latter has a northern extension. 



ZONE VI., forming the lowest declivity of the shore-incline, and a great 

 part of the bed of the Gulf, including a number of channels and larger bays, 

 extending from 20 to 45 fathoms' depth, in which respect, as also to some 

 extent also in character, it corresponds with Professor Forbes' coralline zone. 

 Rocky precipice, whose base consists to a great extent of stone fragments 

 and debris; bed chiefly loam, or clay; springs from the limestone rock 

 below, influencing the degree of saltness, and the temperature of the 

 water ; influence of light reduced to a minimum, but the difference between 

 day and night still perceptible; pressure at 30 fathoms, 6*35 atmospheres; 

 absolute quiescence of waters ; change of temperature slow, and the difference 

 between the extremes 16-18 F. 



The characteristic forms of the Mediterranean flora vanish, and there 

 remain for the most part only general Atlantic, Celtic, and Scandinavian. 



