460 Linruean Society. 



the Helices. 'J'he author gives moderately long and complete com- 

 parative descriptions of 3 species of Anostoma, 2 Tomigerus, 24 Stre- 

 ptaxis, 6 Proserpina, and 1148 species of Helix, with their synonyma 

 most carefully and completely elucidated. It forms one of the most 

 important additions which have lately been made to the study of 

 shells. 



Malacologically considered, the work must be regarded as a retro- 

 grade movement : the author is a pure conchologist, belonging to the 

 same school as Klein, Montfort and Schumacher, for he pays little or 

 no attention to the animal, and even refuses to adopt genera formed 

 on the study of them : if the same system was followed with regard 

 to the marine mollusca, several groups which are now considered as 

 families, each containing several generally adopted genera, must be 

 reduced to a single genus. In the same manner, the immense num- 

 ber of kinds of Helices are arranged together in an artificial manner, 

 without any attention to their relation to one another, which is more 

 to be regretted, asFerussac in his ' Prodromus' arranged the species 

 which he knew in most excellent natural groups ; but Dr. PfeifFer 

 appears to be quite destitute of the faculty of distinguishing or cha- 

 racterizing natural groups, though he describes the species so well. 

 It was the remarkable union of these qualities in the same individual 

 which so eminently distinguished Linnaeus, Jussieu and Lamarck 

 from other naturalists, and causes the great value of their works. 



A large proportion of the species are described from the English 

 collections, and where the author has not observed the species him- 

 self, he quotes descriptions given by its original describers. 



PROCEEDINGS OF LEARNED SOCIETIES. 



LINNiEAN SOCIETY. 



Feb. 15, 1848. — The Lord Bishop of Norwich, President, in theChair. 



Read a memoir ** On the early stages of the Development of Le- 

 manea jiuviatilis, Agardh." By G. H. K. Thwaites, Esq. Commu- 

 nicated by the Rev. M. J. Berkeley, F.L.S. 



Mr. Thwaites attributes the neglect of the early condition of this 

 conferva to its having been confounded in this stage with Trente- 

 pohlia pulchella /S. chalybea, Harv., with which it is frequently found 

 growing intermingled. He states that it may be observed in great 

 abundance towards the end of November, covering the surface of 

 stones with a uniform, dark olive, somewhat villous coating, and 

 adhering with great pertinacity by means of its minute roots. The 

 structure of the plant at this early stage is found to consist of nu- 

 merous conferva-like filaments, of about a line in length and spa- 

 ringly branched. Each filament is about yyV o^h of an inch in dia- 

 meter, and consists of a single row of cells, which are from 4 to 6 

 times longer than wide, and have a blue-green endochrome arranged 



