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Vol. IV. JUNE, 1895. No. 6. 



SOME CAUSES OF THE DISINTEGRATION 



OF SHEIvIvS. 



BY MISS R. HENSMAN. 



(Read before the Dublin Naturalists' Field Club, nth December, 1894.) 



Thk disintegration of shells was, until quite recently, looked 

 upon as due to the friction of the sea, which carries un- 

 inhabited shells backwards and forwards, bringing them into 

 intimate relations with the land and dashing them against each 

 other and against the rocks on the coast, and also to the 

 gradual solvent action of the carbonic acid dissolved in the 

 water. The aim of my paper is to draw attention to another 

 and remarkable cause of this disintegration. The presence 

 of tube-like structures in shells, corals, fossil fish-scales, and 

 other calcareous bodies has been known for some years, but 

 it was not known until quite recently to what cause these 

 tubes were to be attribitted. In 1888 was published a short 

 paper b}^ Bornet and Flahault in the Journal de Bota7iique 

 describing two of these tube-like structures as perforating 

 algse. A year later a fuller paper entitled " Sur quelques 

 Plantes vivant dans le Test calcaire des Mollusques" was 

 published by the same authors, in which ten species were 

 described and illustrated. 



We have six species recorded in Ireland. The first to be 

 found was Gomontia on the shores of Gal way Bay, in the 

 spring of 1891, by Prof. T. Johnson. Owing to the difficulty 

 of freely examining these plants and the little general attention 

 that has been paid to them, we may feel sure that more will 

 be noticed on the Irish coasts, and even fresh forms dis- 

 covered when greater research has been made. So far none 

 are recorded from the North of Ireland. The brown seaweeds, 

 which are as yet unrepresented, we may expect to be recorded. 



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