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SCIENCE-GOSSIP. 



THE SHELLS OF THE ISLE OF MAN. 

 By Lionel E. Adams, B.A. 



'"PHE fauna and flora of any island always have a 

 particular interest ; and the Isle of Man, so 

 easy of access, has a special claim for attention 

 in being a link in the now broken chain of land 

 between Britain and Ireland. Whether it was 

 formerly a link, or always an island in the great 

 lake now forming the Irish Sea, is an unsettled 

 question. It is not, however, the object of this 

 paper to deal with the many problems which the 

 island affords, but to treat briefly of the molluscan 

 fauna. No mention of the natural history of Man 

 can be complete without the mention of Edward 

 Forbes, the distinguished naturalist, who worked 

 the island so thoroughly. His " Fauna Monensis," 

 published in 183S, contains the first catalogue we 

 have of the shells of the island. Of course, 

 numerous additions have been made to this, which 

 will be alluded to ; but it is noteworthy that several 

 of his localities hold true at the present day. 



It is only within recent years that systematic 

 conchology has taken its place as a recognized 

 popular science. I say systematic, for the custom 

 of picking up shells on the sea-shore dates back 

 to antiquity. Most people have had the experience 

 of an unsystematic collection, consisting of all 

 the shells to be found on the sea-beach — poor 

 weather-beaten specimens, too disreputable for 

 their native element to have any further connec- 

 tion with. Then, after trying to separate them into 

 specific heaps, the would-be collector comes to the 

 conclusion that there are only some half-dozen 

 sorts to be found, and gives up collecting as a 

 failure. Yet a very slight acquaintance with the 

 habits of the fascinating sub-kingdom, the Mollusca, 

 would enable the most casual observer to find the 

 objects of his desire where otherwise he would not 

 have thought of seeking. The mere collecting of 

 shells and admiring them when labelled and 

 placed under glass in a cabinet is, of course, worth 

 living for ; but to watch the living animals moving 

 about more than doubles the previous interest in 

 the shells themselves. Granted this slight know- 

 ledge of the habits of the Mollusca, it is rare that 

 shell-collecting, whether by sea, river, pond, or 

 land, does not become a passion. 



Marine Shells. 

 First, to speak of the stores of the ocean. As 

 might be expected, we find differently constituted 

 beings under different conditions, and therefore, 

 according to the depth of water, or the occasional 

 exposure to the air, we find different sorts of 

 inhabitants. The naturalist Risso has marked off 

 four conventional zones of depth as follows : 



(1) The Littoral Zone, which includes that 

 portion of the coast between high- and low-water 

 mark. 



(2) The Laminarian Zone, which extends from 

 low-water mark to the depth of ten fathoms. 



(3) The Coralline Zone, from ten to twenty 

 fathoms. 



(4) The Deep-Sea Zone, including all depths 

 greater than fifty fathoms. 



The first of these, the littoral zone, furnishes 

 all those shells found on sand and among the rock 

 pools at low water — the limpet tribe, the winklet 

 and the larger bivalves. To the ordinary collector 

 this is the most important zone, since it is the 

 most accessible. For deep water the best possible 

 means of search is, of course, the dredge. It is 

 always easy to go out in a trawler or an oyster- 

 dredger, and specimens obtained in this manner 

 direct from the sea far surpass in perfection those, 

 washed up on the beach. There is also a method 

 which will not at first recommend itself to many, 

 but which is productive of excellent results. This 

 is to examine the stomachs of cod fish, etc. .which are 

 thrown away as refuse when the fish are brought 

 ashore and cleaned. At the bottoms of the boats, 

 too, a number of small shells may be found which 

 have fallen out of the dredges or crab-pots. 



Though the dredge is indispensable for obtaining 

 the deep-w^ater species, the Isle of Man possesses 

 more really good spots for low-tide collecting than 

 one usually meets with along the same length of 

 coast-line. Port Erin is especially suitable for this 

 work. At low spring-tides, from the Little Harbour 

 to the further side of the breakwater, the rock-pools 

 are prolific in Rissoa, Trochus, Shenea and Acmaea 

 testudinalis. The shore opposite the Calf of Man is 

 another good spot. Lutraria and Solen vagina are par- 

 ticularly fine along the middle of the bay. Saxicava 

 and My a are plentiful and fine. Near the Stack 

 Rock, by Port St. Mary, there is a flat ledge of rock 

 covered with the most splendid Patella vulgaia var. 

 athietica I have ever seen. These are often very 

 large, deeply coloured inside, and of very irregular 

 growth. They are frequently deeply encrusted with 

 nullipore. The holes which they make for them- 

 selves in this rock are remarkable, the apex of the 

 shell being often considerably below the level of 

 the rock. 



The low, flat expanse of sand at Ramsey beach 

 should be visited after a gale. Great quantities of 

 seaweeds are then washed up, and among their roots 

 I have often reaped an abundant harvest of the 

 smaller shells that are only found, as a rule, dead 

 and weathered on the shore. Pecten pusio may be 



