PUPA. 241 



what of an ellipsoid form. The whorls are also more 

 compact than in BuHmus ; and the mouth is usually 

 fm'nished in the present genus -wdth transverse plates or 

 teeth, instead of the outer lip being merely thickened 

 hy tooth-like tubercles, or of there being a similar protu- 

 berance on the columella, as is sometimes the case in 

 the former genus. The main characters of both these 

 genera, however, are nearly the same, as regards their 

 habits as well as the body and shell. 



The curious processes, called "teeth," which fence 

 in and contract the mouth of the shell in Pupa, are of 

 different kinds. In P. secale they form plate-like ridges, 

 which extend some way into the interior. In P. um- 

 bilicata and P. ringens the adult have either a simple 

 tooth on the columella and a spiral plate on the pillar lip, 

 or else several plate-like ridges as in P. secale, although 

 shorter and more curved ; but, in P. umbilicata and 

 P. ringens, the young have a much more complicated 

 apparatus. This consists of two long spiral ridges like 

 the worm of a corkscrew, one on the pillar lip and the 

 other on the pillar itself, besides a short transverse 

 plate or septum on the outer lip, which is reproduced at 

 intervals. In P. marginata the mouth is often furnished 

 with a denticle or small tubercular tooth on the pillar, 

 and sometimes also with a similar process inside the 

 outer lip ; but it never has the plate-like ridges which 

 are found in the other species. All these various pro- 

 cesses appear to be formed in the same way, \dz. by folds 

 of the mantle secreting the testaceous matter in excess 

 and applying it to- particular parts of the shell. 



Two species of Pupa (viz. tridens and doliolum) have 

 lately been found in the North of France ; and it is 

 therefore not unlikely that they may be found in this 

 country. 



