yinali/iical Notices of Books. 259 



of river shells of the Family of Ostreacew to the catalogue of those 

 already known as inhabitants of fresh-water. 



If to the Families of Cyclad(B and Naiadw, or bivalve shells 

 belonging exclusively to rivers and lakes, be added two genera of 

 Mytilidce^ (Mytilus and Modiola) ; one genus of CorbulidcB, (not 

 yet named ; one genus of Chamacece, (Etheria) ; one of Mactridce^ 

 (Nucula); and one genus of Ostreacew, (Mulleria) ; a catalogue 

 will be formed of all the Genera of Bivalve Molliisca, hitherto 

 known to inhabit fresh-water. Does not this prove the absolute 

 necessity of Geologists becoming thoroughly acquainted with at 

 least all the Genera of Shells, before they undertake to determine 

 the nature of any formation containing fossil remains of Shells ? 

 Is it not a fact that will help to establish the truth of some obser- 

 vations I formerly made upon the real nature of a bed, said by 

 Geologists to be marine, and which is interposed between two 

 others of undoubted fresh-water origin ? Does it not, in fact, 

 prove that we are yet in the infancy of our knowledge of the 



Natural Sciences, particulary as it respects Geology ? 



G. B« S. 



Art. XXXVIII. Anulylical Notices of Books. 



Monographia Tenthredinelarum, Sijnonimia extricata. Auc- 

 tore Am le Peletier de Saint- Far genu, Socielalis Pari' 

 siensis Jlistorife Nuturalis Memhro. 8ro. Paris, 1823. 

 p.p. 176. 



We can never hope to be thoroughly acquainted with the 

 species of Insects but through the medium of Monographs, and 

 we do most sincerely wish that Entomologists would keep this in 

 view; but we must beg to observe, that merely collecting the 

 scattered descriptions of the Insects composing a group or family, 

 can never be deserving the name of a Monograph, nor will nnich 

 credit ever be attached to him, who is a mere compiler, especially 



