Marine Fauna of Great Britain. 407 



fered with. Its back is speckled brown and white, while the 

 border of each segment is reddish. The eyes are prominent, 

 large, and black. When crawling it presents a strange 

 appearance indeed, as if it had a crinoline. 



The occurrence of pigmy forests of Crista ehurnea under 

 stones between tide-marks instead of the zoophyte Sertularia 

 pumiJa at St. Andrews forms a contrast, as also is the frequency 

 of Retepora Beaniana in the deeper water. 



The abundance of borers in wood and the comparative 

 absence of borers in rocks is another marked feature. The 

 only examples of rock-borers lurked between stones that had 

 been fixed by a Laminarian root, in the interstices of the latter 

 on rocks, and in peat, never in an independent tunnel in the 

 rocks. The drift-wood is almost universally perforated by 

 the ship-worm {T'eredo tiorvegica and T. megotara), and 

 since his barren country compels the islander to depend on 

 such for almost every available purpose to which wood is 

 applied, the investigator may well be conversant with the 

 labours of these shell-fishes. Other notable bivalves between 

 tide-marks are Tapes decussata, Area tetragona, and Pecten 

 varius var. nivea^ while the frequency of oysters fixed to 

 stones is characteristic. Lima hians^ so often met with 

 in the Clyde area, is absent, the rarer Lima subauriculata 

 alone being procured by the dredge. The valves of Pecten 

 maximus cast ashore by storms are still used for skimming 

 milk and scooping butter*. 



Between tide-marks Trochus zizyphinus in fine condition 

 abounds at the verge of low water, hanging on the blades of 

 the Fucij but it is not so often met with in dredging as 

 T. cinerarius. Trochus umhilicatus is rather less common 

 than at Tobermory and other parts on the west coast, but it 

 is not rare between tide-marks. All these places, however, 

 differ materially from St. Andrews, where Trochus cinerarius 

 is the only one met with in the same region. Doris pro xima 

 is often seen on the floating blades of the Fuci at low water. 

 The prevalence of Fissurella and Emarginula between tide- 

 marks, of the Eissow, Akera bullata, and Phasianella in the 

 inshore waters, and of the pelagic lanthina with its peculiar 

 float, is noteworthy. 



No greater contrast to the eastern shores exists in any 

 group than in the Ascidians. On the latter only the com- 

 pound forms and a few solitary ones under stones occur 

 between tide-marks ; here in the tidal region are large com- 

 pound forms, such as Aplidium, Amouroucium, bright orange 

 Leptoclinij Botryllus^ and Botrylloides, and numerous solitary 

 * Further south, as at Southport, Ceratisolm legumen is diagnostic. 



