Bibliographical Notices. 



469 



From the inspection of the above table, it appears that the genus 

 Chonetes attained its greatest development in the carboniferous 

 system ; it is there also that the species present many varieties of 

 form and are of the greatest size. This latter remark applies also 

 to Productus, to which Chonetes is closely allied. However, the pro- 

 portion in which this development has taken place is very different 

 for the two genera. With regard to their distribution in time, the 

 following conclusions are drawn from the table above quoted : the 

 two Silurian species belong to the upper beds of the system ; in the 

 Devonian system the C. Falklandica, sarcinulata and dilatata cha- 

 racterize the inferior beds, the C. crenulata, nana and setigera are 

 characteristic of the middle portion, and the G. armata^ minuta and 

 convoluta are found only in the upper beds of the same system. The 

 C. concentrica, papilionacea, comoides, Shumardiana, Dalmaniana, sul- 

 cata, Buchiana and tuberculata belong exclusively to the inferior 

 beds of the carboniferous system, the C elegans to the middle, and 

 the C. Laguessiana and perlata to the superior beds of the same 

 system ; and lastly, the C. variolata belongs to different carboniferous 

 deposits, and appears even to pass into the Permian system. 



In a memoir of this nature, it is almost impossible to attain abso- 

 lute correctness, more especially from the author not having had the 

 means of verifying all the species from original or well- authenticated 

 specimens ; independently, however, it is a work of great research, 

 and will be of considerable value to the palaeontologist, in placing 

 before him carefully executed figures of the species belonging to 

 these two genera. The volume is in quarto, illustrated by 20 plates, 

 and contains also an alphabetical, synonymical and chronological 

 table of all the species. 



Monographia Heliceorum Viventium, sistens Descriptiones systematicas 

 et criticas omnium hujus familiee generum et specierum hodie cogni- 

 tarum. Auctore Ludovico Pfeiffer, Dr. Cassellana. Fasc. 1,2,3. 



Lipsi^, 1847-48. 



It is with great pleasure we announce the appearance of the com- 

 pletion of the first volume of this excellent monograph, containing 



