336 Professor Edward Forbes on the 



be the extent of rise and fall of the tide, this zone, wherever 

 the ground is hard or rocky, thus affording security for the 

 growth of marine plants and animals, presents similar 

 features and can be subdivided into a series of corresponding 

 sub-regions ; through all of which the common limpet {Patella 

 vulgata) ranges, giving a character to the entire belt. Each 

 of these sub-regions has its own characteristic animals and 

 plants. Thus the highest is constantly characterised by the 

 presence of the periwinkle, Littorina rudis (and on our 

 Western shores, Littorina neritoides), along with the sea-weed, 

 Fucus canaliculatus. The second sub-region is marked by 

 the sea-weed Lichina and the common muscle {Mytilus edulis.) 

 In common with the third sub-region it almost always presents 

 rocks thickly encrusted with barnacles, so that where our 

 shores are steep, a broad white band entirely composed of 

 these shell-fish, may be seen when the tide is out, marking 

 the middle space so conspicuously as to be visible from a great 

 distance. In the third sub-region the commonest form of 

 wrack or kelp {Fucus articulatus) prevails, and the large 

 periwinkle {Littorina littorea) with Purpura lapillus are domi- 

 nant and abundant. In the fourth and lowest sub-region the 

 Fucus just mentioned gives way for another species, the 

 Fucus serratus ; and in like manner the shells are replaced 

 by a fresh Littorina {littoralis) and peculiar Trochi. 



Once below low-water mark the periwinkles become rare, 

 or disappear, and the Fuci are replaced by the gigantic sea- 

 weeds known popularly as tangles (species of Laminaria, 

 Alaria, ^c.) among which live myriads of peculiar forms of 

 animals and lesser plants. The genus Lacuna among shell- 

 fish is especially characteristic of this zone. In sandy places 

 the Zostera or grass-wrack replaces the Laminaria. The 

 Laminarian Zone extends to a depth of about fifteen 

 fathoms, but in its lowest part the greater sea-weeds are 

 comparatively few, and more usually the prevailing plant is 

 the curious coral-like vegetable called Nullipore. 



From 15 to 50 or more fathoms we find a zone prolific in 

 peculiar forms of animal life, but from which conspicuous 

 vegetables seem almost entirely banished. The majority of 

 its inhabitants are predacious. Many of our larger fishes 



