Polythala mian from Transylvania. 



353 



The results of the measurement of ten individuals are 

 brouo-ht toirether in the folio win o- Table : — 



From this Table it appears that the largest of the 16- 

 cliambered individuals measures 0*42 millim., and that the 

 size of the shell gradually decreases in accordance with the 

 diminution in the number of the chambers, so that the smallest 

 6-chambered shell measures only 0"08 millim. Further I 

 may note that the transverse diameter of the first chamber of 

 the second whorl in all the measured shells has the same 

 length of 0'08 millim., and that the diameter of the primordi-al 

 chamber measures 0*04 millim. in all the shells. The greatest 

 variation naturally occurs in the transverse diameter of the 

 last chamber; but in individuals with an equal number of 

 chambers this is also equal, only one 16-chambered shell 

 forming an exception, in which the last chamber possesses a 

 length of 0'18 millim., measuring, of course, from the inaer 

 margin of the whorl to the outer wall of the chamber. 



However, I did not make measurements only of the pri~ 

 mordlal and last chambers, but also of the other chambers, 

 and from these it appeared that the corresponding chambers 

 in all individuals possess nearly the same size, the variations 

 being so minute as hardly to deserve mention. 



The numbers furnished by the measurements, I think, are 

 in favour of the assumption, which is a ^?r«'ori correct, that 

 the 6-, 10-, 12-, 13-, and 14-chambered individuals can only 

 belong to the developmental series of the 16-chambercd speci- 

 mens, and I do not hesitate in the least to express this 

 opinion. 



As regards the form of the chambers I may sum up as 



