Royal Physical Society. 11 



upon insulated species, while from some peculiarity of habitat, or some 

 hardiness of constitution, their cogeners escape. There are two species 

 of Solen in the Firth, S. siliqua and S. ensis ; but we have not seen, on 

 the present occasion, a single dead individual of the latter species ; and, 

 of at least four species of Mactra, Mactra stultorum seems alone to have 

 suffered." 



He had, since the appearance of the above, several times visited the 

 shores in the neighbourhood of Leith and Portobello, and now craved 

 leave to bring before the Society a few additional facts. Up till Friday 

 last, the dead shell-fish, consisted almost exclusively of the two kinds spe- 

 cified in the paragraph, — Solen siliqua and Mactra stultorum. Since 

 that time, however, considerable numbers of the smaller molluscs have 

 also been thrown up dead upon the beach ; and their later appearance, 

 as he found their remains mingled with very young specimens of the de- 

 stroyed Solen and Mactra, may have been the result rather of a mecha- 

 nical than of what he might term a constitutional cause. The greater 

 shells have been first driven ashore, from the circumstance, mayhap, that 

 they presented a larger surface to the waves, and then the smaller, in- 

 cluding, in considerable proportions, the young of the large ones. Among 

 the lesser molluscs, destruction seems to have fallen more extensively on 

 that delicate shell Tellina fabula than on any of the others. Tellina 

 tenuis has also suffered, but to a much less extent. Next to Tellina fa- 

 bula, the mollusc of the smaller species that, in proportion to its number, 

 has been most extensively destroyed, seems to be Donax anatinus. 

 Every little pool has its numerous specimens of this shell lying gaping 

 and dead. He observed also a few recently killed specimens of Mactra 

 subtruncata, but, considering the abundance of the shell on our sandy 

 flats, only a very few ; and also, what he had not seen in his previous 

 walks, a few individuals of Solen ensis, but scarcely in the proportion of 

 one to a hundred of its cogener Solen siliqua. There were localities, 

 too, — as immediately below the town of Portobello, — in which he found 

 great numbers of the slim and delicate shells of Syndosmya alba still in- 

 closing the dead molluscs. Among the univalves, he picked up a consi- 

 derable number of lately destroyed specimens of Natica monilifera, 

 There seems to be a peculiar circumstance in the history of this shell 

 which still requires explanation. Fully nine-tenths of the specimens 

 thrown ashore on our Leith and Portobello beaches, in a dead or dying 

 state, have their lip edges fractured and broken, the gaps often im- 

 pinging deeply into the inner space of the shell occupied by the mollusc. 

 Of ten individuals of this species which he picked up on various parts of 

 the beach on Saturday last, all exhibited the broken lip ; of twice that 

 number picked up on Monday, only three had the lip entire ; and as much 

 weaker shells come unbroken to the shore, the mutilation must, he sus- 

 pected, be regarded as the work of some unknown enemy. But the enemy 

 which had killed these naticas was evidently the frost. Besides the mol- 

 luscs, some of the commoner crustaceans of our coasts appear to have suf- 



