184 Reports and Proceedings. 



Carpenter, M.D., F.E.S. ; William Carruthers, Esq., F.L.S. ; W. 

 Boyd Dawkins, Esq., M.A., F.E.S. ; Prof. P. Martin Duncan, M.B., 

 F.E.S. ; Sir P. cle M. G. Egerton, Bart., M.P., F.E.S. ; John Evans, 

 Esq., F.E.S., F.S.A.; David Forbes, Esq., F.E.S.; J. Wickliam 

 Flower, Esq.; Capt. Douglas Galton, C.B., F.E.S.; E. A. C. 

 God win- Austen, Esq., F.E.S. ; J. Wliitaker Hulke, Esq., F.E.S. 

 Prof. T. H. Huxley, LL.D., F.E.S. ; J. Gwyn Jeffreys, Esq., F.E.S. 

 Sir Charles Lyell, Bart., D.C.L., F.E.S.; C. J. A. Meyer, Esq.: 

 Prof. John Morris ; Joseph Prestwich, Esq., F.E.S. ; Prof. A. C 

 Eamsay, LL.D., F.E.S. ; E. H. Scott, Esq., M.A., F.E.S. ; Prof. J 

 Tennant, F.Z.S. ; Eev. Thomas Wiltshire, M.A., F.E.A.S. ; Henry 

 Woodward, Esq., F.Z.S. 



n. — Geological Society of London. — February 22, 1871. — 

 Joseph Prestwich, Esq., F.E.S., President, in the Chair. The follow- 

 ing communications were read. 



1. "On supposed Borings of Lithodomous MoUusca." By Sir 

 W. C. Trevelyan, Bart., M.A., F.G.S. 



The author referred to Mr. Mackintosh's paper on this subject 

 (Quart. Journ. Geol. Soc. vol. xxv. p. 280), and stated his conviction, 

 from examination of specimens, that the holes in question are the work 

 of Helices, or other terrestrial Mollusca. He ascribed the same origin 

 to the so-called " P/^oZas-borings " in the limestone at Orme's Head 

 and elsewhere. He considered length of time to be a necessary 

 element in the formation of these holes. The author also remarked 

 that he. had suggested a glacial origin for the terminal curvature of 

 the laminae of slate-rocks as early as 1849. 



Discussion. — Mr. Gwyn Jeffreys read extracts from a work published by the Eev. 

 Mr._ Hodgson in 1827, on the Natural History of Northumberland, in which these 

 borings in limestone were referred to the action of snails. Mr. Jeffreys considered 

 the foot to be the sole instrument employed by the boring Mollusca in excavating 

 their burrows. He exhibited specimens of Lias from Lyme Regis perforated by 

 Pholas, and of hard limestone from Malta perforated by Lithodomus, and remarked, 

 in connexion with the notion that asperities on the shell might be boring agents, that 

 the shell of Lithodomus is perfectly smooth. 



Professor Ramsay mentioned that he had seen Helices taken out of these holes at 

 Tenby by Dr. Buckland, who believed that the snails effected the perforations by the 

 agency of an acid. 



Mr. Charlesworth thought that if so much uncertainty could prevail upon such a 

 subject, it threw great doubt upon some of the grandest generalizations of geology. 

 He referred to the evidence connected with the glaciation of the Great Orme's Head, 

 in which the origin of the perforations under discussion was of much importance, Mr. 

 Darbishire maintaining that they were the work of Pholades, while Mr. Bonney 

 asserted that they were produced by snails. In the same way the origin of the 

 celebrated borings in the Temple of Jupiter Serapis might be disputed, and the 

 generalization founded upon it rendered doubtful. Mr. Charlesworth noticed the 

 necessarily small proportion of borers to the whole snail population of Britain, and 

 remarked especially upon the absence of perforations in the Chalk districts. He con- 

 sidered that repeated observations were necessary before this snail-engineering could 

 be admitted, and suggested a systematic course of experiments. 



_Mr. Boyd Dawkins suggested that the carbonic acid exhaled by snails in respiration 

 might act upon limestones, and remarked that chalk weathers too rapidly to preserve 

 the excavations. 



2. "■ On the probable Cause, Date, and Duration of the Glacial 



