234 



SHELLS AND SHELL-FISH. 



PART I. 



that his C. trocMformis would he hetter placed in that 

 family. But even the errors of such a man are as 

 lights to others ; for when douhts exist as to the limits 

 of a genus, we may be perfectly sure of the passage, 

 and that both genera are natural. On the other hand, 

 if we look to the resemblance between Patella and 

 CalyptrcBa as analogical, these conflicting opinions are 

 at once reconciled : both are cup-shaped, pyramidical, 

 and with the apex almost central ; and that both stand 

 opposite to each other in their respective circles, the 

 intelligent reader will perceive if he brings these fa- 

 milies into comparison. 



(217.) The next group, which, from a consideration 

 of the animal, we have here named Cheltnotus, cor- 

 responds, in some measure, to Sigaretus of authors. 

 We find it impossible, however, to understand this 

 group. It has been customary to place in Sigaretus 

 nearly all those ear-shaped shells of the same form as 

 Stomatia, but which are not perlaceous, without a 

 knowledge of their animals, or, even when that was 

 obtained, without a due regard to the differences they 

 exhibited. We mention this, not as conveying censure, 

 but as the probable reason why we cannot unravel this 

 exceedingly intricate question. This has partly arisen, 

 strange as it may appear, from the new light thrown 

 upon the JVaticce by Guilding. The beautiful delinea- 

 tions he has made of the animal of a typical species, 

 shows that it is almost an internal shell, or at least 



