OF EVOLUTION. 93 



occupied by the tubercles of M. corona ; 

 conversely, in many of the less typical forms of 

 the latter there is a close approximation to the 

 condition found in M. subcoronata. In this 

 manner the two species are inseparably bound 

 together. As in the case of the stromb, so in 

 this instance also, no trace (or at best but 

 a doubtful one) of the recent Melongena has 

 been found in the deposits containing the fossil; 

 nor, on the other hand, have any traces of the 

 latter been found in the modern seas, so that we 

 may here also plausibly assume that the one form 

 is the forerunner and probable progenitor of 

 the other. 



The fossil volute differs slightly in outline 

 from the rare living species of the coast, and is 

 further distinguished from it by its more acute 

 apex, and the greater prominence of the costal 

 ornamentation on the apical portion of the shell. 

 These differences, although not very great, nor 

 seemingly of much consequence, are yet per- 

 sistent, and as such may be considered of 



