Marine Fauna and Fishes of St. Andreivs. 141 



countless swarms of Salpce, Velellce, Medusa;, and other forms 

 to die on the beach. 



The tidal rocks, again, which are mostly covered by sea- 

 weeds, present a varied and prolific site for many species. 

 The rock-pools are both frequent and picturesque ; and they 

 possess many undisturbed stones, often of large size, the under 

 sui'faces of which are most favourable for the growth and 

 shelter of numerous forms — though of course they cannot be 

 compared in this respect with the littoral stones at Herm, which 

 have a profusion of rare crabs, annelids, ormers and other 

 moUusks, polyzoa, hydroids, and the yellow, red, purple, green, 

 and white sponges. The soft sandstone and shale afford an 

 ample field for the perforations of Pholas crispata, Saxicava 

 rugosa, and Leucodore ciliata. The fissures and chinks of 

 the rocks, moreover, as on almost every part of the British 

 shores, give shelter to a large number, especially the annelids, 

 which find in the muddy or sandy crevices a safe retreat for their 

 soft bodies, slender tubes, or muddy tunnels, and opportunities 

 for capturing sufficient food at the free margin of the rock or 

 from the ingoing currents. It is chiefly in such localities that 

 Sipunculus Johnstoni and swarms of Leucodore and Nicomache 

 occiu", while Nereis cultrifera, Eidalia, Syllisj and the nemer- 

 teans are also common. Occasionally an Idotea is met with ; 

 but the general absence of the isopods in these crevices dis- 

 tinguishes them from those in the gneiss of the south and 

 west, as in the Channel Islands and the Outer Hebrides — 

 and especially from the former by the absence of Pilumnus 

 hirtellus, Area, the Sabellidce, the Funicidce, and their allies. 

 To these fissures certain boring annelids and Saxicava chiefly 

 retreat when the rocks do not afford a suitable medium for 

 their perforations — though at St. Andrews there is free scope 

 in this respect, from the sandstones and shales so soft as to be 

 pitted deeply by the common limpet to those nearly as dense 

 as granite. 



The sea-margin at St. Andrews, like other parts of the 

 east coast of Scotland, presents decided differences when 

 contrasted with the northern, soutliern, and western shores, 

 though many forms are common to all. Thus the laminarian 

 zone at St. Andi'ews is much less luxuriant than that of the 

 Zetlandic waters with the fine forests of gigantic tangles, 

 amidst which there is a galaxy of animal life. The vegetation 

 of its littoral zone is surpassed by the rich Fuci of the tidal 

 rocks and the trailing masses of Chorda Jilum on the surface 

 of the sea immediately beyond low-water mark in the Outer 

 Hebrides. Its marine forms are placed under very different 

 circumstances from those in the quiet voes of West Shetland, 



Ann. & Mag.N. Hist. Ser. 4. Vol. xiii. 11 



