THE EUROPEAN SEAS. 



93 



Mediterranean, creeping on the sand, and burying 

 in it near low-water mark, often in company with 

 Donacilla Lamarchii, also a Finisterre shell ; Area 

 barbata and Lima squamata, Mediterranean bivalves 

 that live among rocks close to the water's edge : 

 Triton nodiferum and cutaceum, whelks of a genus 

 that has no representatives elsewhere in the Celtic 

 province, and Trochus Laugieri, a sublittoral shell, 

 not noticed further to the north. It is worthy of 

 remark that the greater number of these species are 

 dwellers on the verge of low-water mark, either above 

 or below it. Moreover, they are mostly rock-shells, 

 so that their presence here, separated frequently as 

 they are from their brethren by the sandy shores of 

 the southern half of the Bay of Biscay, is an 

 anomaly not easy, at least by ordinary causes, to 

 be accounted for. 



Everywhere around the British shores the subdi- 

 visions of the littoral zone are strikingly marked by 

 both animals and plants, especially on the more 

 rocky portions of the coast. It matters not how 

 great or how small may be the fall of the tide ; the 

 several belts of the zone are equally well distin- 

 guished where there is a very small and where there 

 is a very considerable fall. There are local differ- 

 ences, especially noticeable when we compare the 

 eastern with the western provinces, or the extreme 

 north with the extreme south ; but in the main the 

 belts or subordinate zones are characterized by the 

 same species throughout. Thus, the highest of them, 



