NOTICES OF SERIALS. 27 



from the appearances we have just described. In the Brachyura, where the organs 

 are most fully developed, there is attached to the operculum a long, osseous tendon 

 or lever, by which the attached muscles raise or close the entire organ, but there 

 is no internal structure of any kind which could identify it as "being an organ of 

 sound. The aqueous sac mentioned by Edwards, I have entirely failed to discover. 

 Viewing the two antennae each as a whole, in their relative positions and con* 

 nection with the rest of the animal, we are forcibly led to the conviction that the 

 tipper antenna is an organ of hearing, and the lower antenna is an organ of smell." 

 The author's views are illustrated by plates. (M. de Quatrefages) On Double Mon- 

 strosity in Fishes. Proceedings of Learned Societies Linnean Society, De- 

 cember 5, 1854, W. Yarrell, Esq., V.P., in the Chair ; December 19, T. Bell, 

 President, in the Chair. Zoological Society, February 14, 1854, Dr. Gray, Vice- 

 President, in the Chair ; read, notes on the habits of Indian Birds, by Lieutenant 

 Burgess; February 28, 1854, Dr. Gray, Vice-President, in the Chair. Koyal 

 Institution of Great Britain, April 20, 1855., W. R. Grove, M.A., Q.C., F.R.S., 

 Vice-President, in the Chair. Botanical Society of Edinburgh, April 12, 1855, 

 Professor Balfour, President, in the Chair. Miscellaneous Nereis bilineata, by W. 

 Thompson ; On a New Species of Thallasidroma, by G. R. Gray, F.L.S., and F.Z.S. ; 

 On the Eggs of Otogyps and Prosthemadera, by H. F. Walter. Meteorological 

 Observations and Table for May, 1855. 



No. 92, August: (T. R. Jones, F.G.S.) Notes on Palaeozoic Bivalved Ento- 

 mostraea No. 1, Some Species of Beyrichia from the Upper Silurian Limestones 

 of Scandinavia with a Plate; (J. W. Griffith, M.D., F.L.S.) On the Conju- 

 gation of the Diatomaceae with a Plate; (Thomas Wright, M.D., F.R.S.E.) On 

 a New Genus of Fossil Cidaridae, with a synopsis of the species included therein ; 

 (T. Horsfield, M.D.) Brief Notices of several New or Little-known Species of 

 Mammalia lately discovered and collected in Nepaul, by Brian Houghton Hodgson ; 

 (William Clarke) On the Assiminia Grayana and Rissoa anatina ; (T. Blackwall, 

 F.L.S.) Descriptions of two newly-discovered species of Araneidea ; (J. Gwyn 

 Jeffreys, F.R.S.) Note on the Descent of Glaciers. No less than five various 

 theories have been proposed to account for the descent of glaciers 1st, by De 

 Saussure, who supposed that glaciers descended solely by their own weight ; 2nd, 

 by De Charpentier, and adopted by Agassiz, who supposed that the phenomenon 

 was caused by the surface of the glacier being thawed during the day, that the 

 water thus produced percolated the porous material, and that upon congelation 

 taking place at night, the whole structure expanded in every direction, naturally 

 occasioning or accelerating a downward movement in the direction of the slope ; 

 3rd, that of Professor James Forbes, which attributed it to the viscous or plastic 

 nature of the glaciers, causing the descent suis viribus ; 4th, that of Mr. Hopkins, 

 who referred the motion of a glacier to the dissolution of the ice in contact with the 

 rock ; and, 5th, that of Rev. H. Mosley, who supposed that it was caused by the 

 heat of the sun, and, consequently, to an alternate expansion and contraction of the 

 material. Without either patronizing one or any of these various and seemingly 

 conflicting theories, or attempting to make up " the half dozen," Mr. Jeffreys is of 

 opinion that each and all of the forces above mentioned may have their own part 

 in producing this curious phenomenon ; by this means he reconciles the various 

 theorists, and good-naturedly sets at rest this difficult and vexed question. 



