330 ANNUAL OP SCIENTIFIC DISCOVERY. 



others, so that the dimensions observed in one river are no guide for 

 those in another. All of the large shells found in waters which had 

 flowed for only three or four years might not have grown from eggs 

 deposited there ; mature shells may have crept into such waters. The 

 Unios lay thousands of eggs, in some species very mature, in others 

 less so. 



In answer to an inquiry from Dr. Jackson, whether, from the ascer- 

 tained growth of shells in this manner, it would be possible to deduce 

 the approximative period during which geological strata, composed 

 principally of shells, had been deposited, Prof. Agassiz replied that 

 he was satisfied that nothing could be obtained from such data ; the 

 elements of the problem were not in them. 



DISTORTED GROWTHS IN SHELLS. 



At the meeting of the British Association, 1860, Mr. H. H. Hig- 

 gins stated that the late Mr. Gaskoin, of England, had in his museum 

 a series of specimens, collected for the purpose of illustrating the 

 pathology of the Mollusca. This series was in course of formation in 

 the year 1835, from which period, to the time of his decease, Mr. 

 Gaskoin devoted considerable attention to the selection, from various 

 sources, of specimens of shells in any wise remarkable for distorted 

 growth, or for the repair of injuries received during the life of the 

 animal. In the course of more than twenty years' collecting, Mr. 

 Gaskoin had enriched his pathological cabinet, not only with a great 

 variety of mended fractures and distorted growths, but with many 

 duplicates, sometimes of cases apparently altogether exceptional, and 

 likely to be unique. A select series of specimens was then exhibited 

 to the Section, and remarks were made upon them, which can scarcely 

 be presented intelligibly apart from the specimens themselves. Lon- 

 don Athenceum. 



HABITS OF THE BEAVER. 



The following letter, from Mr. A. H. Smith, of Solano Co., Califor- 

 nia, " On the Habits of the Beaver," was recently read before the 

 Academy of Sciences, Philadelphia : 



" This winter I have had an opportunity of observing somewhat 

 the habits of the Beaver. You know that this cunning little animal 

 is famed for his industry and bold engineering. About the middle 

 of our land there is a large slough seventy feet wide and very deep, 

 running back into the country. In the progress of our work, it 

 became necessary to stop it off and lay a large sluice to drain it, which 

 was done in a complete manner. 



" At the head of the slough, two miles away, the beavers had their 

 settlement. When the water fell away from their houses, and would 

 not return, as usual, they seemed to have sent a delegation down to 

 see what was the matter. For several successive mornings we found 

 a dam built across the race leading to the sluice, quite skilfully made 

 with sticks and tules, and cemented with mud. One of the men 

 agreed to watch for them, with the hope of securing their skins, 

 which are of some value. The night was bright moonlight. Four 



