.«o\\ja'J \o ^^^Bihliographical Notices. .'•' ' 409 



•If I include these last among the fluviatile genera, I should add in, 

 Venus brunnea and Cytherea vulgaris, as they inhabit fresh and salt 

 water alike ; however, as to that, I have foimd Ampullaria glaucal 

 doing the same.' '''vjo .'>v»^"''^'" 6>.U>.ivoA-.v> . -■.^^. ■:'i^"'' • 



Of the marine Mollttsca and thte Cttlsltlifee^;«c,,^T'i;kft givd you no 

 information by name, neither can I in like manner catalogue the Rep- 

 tilia I have ; on these last I have no work whatsoever to supply me even 

 with generic divisions, much less specific. I don't give you the names 

 of any Lepidoptera — those you know as well as I do — better, you 

 ought — as you have the advantage of books and cabinets to refer to. 



Well, my dear friend, my task is ended ; you are doubtless glad of 

 it." if I make any fresh discoveries or glean any zoological news, you 

 shall hear again. 



Meanwhile I remain as ever, yours very truly, 



Edgar L. Layard. 



BIBLIOGRAPHICAL NOTICES. 



The Geological Observer. By Sir H, T. De la Beche, C.B., 

 F.R.S. &c., Director-General of the Geological Survey of the 

 United Kingdom. London : Longmans. 



This work, although differing in its general characters from the ordi^^ 

 nary introductions to geological science, is essentially mtended to ai<i,' 

 the student in his practical observations in the field, and few men have 

 brought so much experience to the task as Sir Henry De la Beche, 

 devotuig, as he has done for a long series of years, an earnest and 

 laborious investigation to the physical changes which have taken .place 

 on the earth's surface. ;. i) ur' 



The ample opportunities which Sir H. De la Beche has enjoyed of 

 comparing the geological constitution of this country with that of 

 many other parts of the globe, noting the pecuharities, differences or 

 resemblances of the various mineral masses, and not overlooking the 

 importance of the causes at present in operation, have materially 

 fitted him to produce such a volume as " The Geological Obsei-yer." 



The previous works of the author are well known, and the title of 

 the present one must not lead the reader to expect merely an ele- 

 mentary treatise or a disquisition on the succession of rock formations 

 and their contained organic remains, but is more usefully occupied 

 in pointing out the importance of a knowledge of those general 

 principles connected with the present terrestrial phsenomena — the 

 changes now taking place on the surface of the globe by igneous and 

 aqueous action — their influence on the distribution of animal and ye;^.. 

 getable life— the formation of strata— the imbedding of the remains 

 of terrestrial and marine beings, and showing their intimate bearing 

 upon the mterpretation of geological discovery ; in fact, it may be con- 

 sidered as a treatise ou applied cosmical phsenomena to the ancient 

 changes of the earth, so as to assist the observer in his inquiries re^" 

 specting the physical geography of the great geologic periods, 6?^ 



