404 Scientific Intelligence — Zoology. 



The diffex'ent substances into which these animals penetrated might 

 require different means. Some species of the genus Pholas bored 

 in wood, some in stone, but none in both. Mr Hancock had referred 

 to a species of sponge, the Clione, as a borer. This animal was un- 

 doubtedly irritable, but he doubted if it made itself the holes which 

 it occupied. Mr Bowei'bank could bear testimony to the irritability 

 of Clione ; but he did not believe that it bored. He believed it to 

 be a true sponge. It has spiculse and tubes like a Halichondria. 

 With regard to the application of the author's theory to the absorp- 

 tion of the columella of shells, he did not think it was necessary, as 

 the researches of Dr Carpenter and himself had shewn that tlie shells 

 of the mollusca were organic and susceptible of absorption. Dr 

 Carpenter had seen in the borders of the mantle of Terebratula, sili- 

 ceous particles, in the form of spines. It was not necessary that the , 

 granules should be silex, as any hard substance would be sufficient 

 for the purpose. He had seen Pholades in such a position in an 

 excavation as to render it impossible that they should have turned 

 round for the purpose of boring. Mr Jeffrey stated that he had ob- 

 served that the tongues of many forms of mollusca were constantly 

 renewed in the manner mentioned by the author, as occurring with 

 the siliceous granules. The President drew attention to a fact stated 

 by Mr Osier, in his paper in the Philosophical Transactions, on the 

 boring of molluscs, that, in one instance, he had observed that the 

 Saxicava rugosa, in boring through a calcareous rock, had been ar- 

 rested in its course by a layer of argillaceous matter, thus lending 

 great support to the solvent theory. — (^Atheneeum, No. 1086, 

 p. 842.) 



To the Editor of the Edinburgh New Philosophical Journal. 



Blaie Logie, Julii 17, 1848. 



Sir, — My attention has been turned, by Sir George Mackenzie, to the fol- 

 lowing sentence in my paper on the Parallel Roads of Lochaber, published in 

 your last Xumber : " Iso attempt, besides, is made, accoiding to this theory, to 

 shew why the various shelves should be expected to stop short at the parti- 

 cular places where, by observation, they are found to do so ;" and to the follow- 

 ing one in his paper published in your Number for October 1847 to January 

 1848 : " I may here remark, that the shelves should be found to terminate near 

 to the locality where it would appear the waters continued to be greatly agi- 

 tated ; and this is seen to be the case." 



Now, although, with all personal respect for Sir CtEORge Mackenzie, and 

 with no wish to detract from the merit of his paper, it appears to me that he 

 do.'s not develop the idea contained in the remark just quoted, or support it 

 sufficiently by reference to the "various shelves" and the "particular places 

 where, by observation, they are found to terminate;" and although I conceive 

 it to be incompatible with the occurrence of the shelves in certain places where, 

 by observation, they are found to exist ; yet, as my sentence would imply, what 

 I did not mean, that he had not referred to what ho conceived might be a cause 

 for their termination, I feel it right, by directing the attention of your readers 

 to what is quoted aljove from his paper, to correct any impression to that effect 

 Avhich ray sentence — through inadventence not expressed with sufficient care — 

 may have produced on their minds. I am, Sir, your obedient servant, 



James Thomson Jun. 



