APPENDIX. 261 



to the breadth ; the extreme width is as often below the middle, 

 as at the middle itself. The rapidly increasing volutions are not 

 flatly shelving as in the Mediterranean examples, but decidedly 

 convex ; the infrasutural retusion of the last-formed whorls 

 though present, is far from conspicuous. The periphery of the 

 body is but little angulated. The volutions of the spire are not 

 remarkably short, the dorsal breadth of the penult turn being 

 for the most part to its length as five to two. The tortuous 

 pillar lip, which does not occupy one half of the total length of 

 the shell, sweeps towards the outer lip in an oblique curve. 



A more than ordinary latitude seems permitted to shape in 

 this species, because the larger turns do not always strictly coil 

 in a regular spiral, but sometimes deflecting attach themselves 

 below the periphery : in which event the spire is wont to become 

 more elevated, and its more rounded turns to swell out in some 

 degree above the suture. 



Vol. iii. p. 2. Neritina. 



In our text the operculum is described as corneo-calcareous. 

 It is really, as Mr. Gray pointed out, solid, calcareous,' and with 

 a thin edge, whilst Nerita has a corneous operculum, lined on 

 each side with a calcareous coat, so that it can be split into two 

 plates. 



Vol. iii. p. 8. Paludina Listeri. 



The same name (vivipara) having been applied to this and the 

 succeeding species, we erroneously located the bandless Paludina 

 taken by Mr. Pickering, as a variety of the former instead of the 

 latter. We withdraw the doubt expressed respecting the Lanca- 

 shire locality, Mr. Glover, of Manchester, an excellent authority, 

 having (as we are informed by Captain Brown) taken it himself 

 near Southport. P. vivipara has been taken by Captain Brown 

 abundantly in the canal near Birmingham. 



