THE NAUTILUS. Ill 



very young of a valid species distinct from both prarosa and sub- 

 globosa, of which A. tintinnabulum was the adult form. 



Subsequently Tryon reviewed Dr. Lewis' paper (Am. Jour, of 

 Con., VII, p. 86) and, without discussing at all the facts on which 

 the latter had based his conclusions, reiterated his former conclu- 

 sions, stating that Mr. Anthony did not find tintinnabulum in the 

 Ohio, but did find cincinnatiensis, and satisfied himself that it was 

 the young of prcerosa and that he, himself, had examined " thou- 

 sands of specimens from many localities " and was " fully convinced 

 that subglobosa and tintinnabulum are the same species." And this 

 position was maintained in his elaborate monograph of the Strepo- 

 matidcB published by the Smithsonian Institution in 1873. 



Since then, so far as I have been able to ascertain, nothing has 

 been published on the subject. 



It is obvious that, if these different forms of Anculosa exhibit as 

 claimed by Lewis persistent and characteristic differences in the 

 young shell, a valuable standard of comparison can be established, 

 which will, when thoroughly worked out, enable us to definitely 

 determine their relationships and their claims to specific or varietal 

 recognition. And although, for a complete solution of the questions 

 of synonymy involved, full suites of all ages of all the different forms 

 would be necessary, any detailed information will be of value, both 

 as leading the way towards the final settlement of the matter and as 

 an incentive to further investigation and systematic work in the 

 field for the acquisition of the material still necessary for successful 

 results. For these reasons, the following notes have been compiled 

 and, with full recognition of the fact that they are necessarily in- 

 complete and quite insufficient for any broad generalizations and are 

 of value only so far as they deal with material under observation, 

 are published with the hope that they may lead others to review the 

 material in their possession and incite additional effort toward 

 securing the missing links. 



I. Anculosa prcerosa Say. PI. X., figs. 1-6. 



Unfortunately I have not been able to obtain any of the minute 

 young of this species from the Ohio River, the smallest specimens 

 seen having passed the carinate stage. But from a comparison of 

 these with those of corresponding size and development from a very 

 complete series of all sizes, ranging from .0125 mm. in diameter to 



