412 PYKAMIDELLID^:. 



be alive in the immediate vicinity ; their numbers, and often 

 fresh and excellent condition, are sufficient proof; and we 

 have offered what may be the solution of the difficulty of 

 obtaining them alive*. 



With respect to the so-called Odostomia turrita of authors, 

 much discussion and difference of opinion have lately existed 

 as to whether it is a distinct species, or a variety of an esta- 

 blished one. It is inferred, from the specimens being more or 

 less spirally striated throughout, that it is a good species. 

 My own opinion has changed more than once : at one time I 

 thought it might be an aberrant variety of Chem. insculpta ; 

 in this I am mistaken : again, I had made up my mind that 

 it could not belong to Chem. acuta ; in this point I am also 

 mistaken, as it turns out to be scarcely a variety of that 

 common species ; it is one of the individuals with the more 

 inflated volutions. I have forty specimens, which I took the 

 trouble separately to submit to the microscope, and in those 

 which were not worn, I was agreeably surprised to receive the 

 solution of this problem, by finding that every recent shell 

 was finely spirally striated throughout ; in some the strise were 

 more apparent, and easily seen by a Coddington lens; in 

 others the microscope was required, and with ordinary powers, 

 even in the most apparently glabrous shells, the spiral lines 

 became conspicuous. In the shells that have not been much 

 rubbed, the strise have acquired a crassitude by exposure to 

 the air, as is always the case, which renders them more 

 visible ; I have such ; but in the perfect recent ones they are 

 excessively fine, and cannot be detected without considerable 

 optical assistance. This is the simple history of the so-called 

 C. turrita, which certainly is nothing more than the Chem. 

 acuta with the strise somewhat more apparent than usual; 

 such are in our cabinet, and malacologists will find that they 

 have not a perfect recent specimen of the C. acuta which is 

 not more or less spirally striated throughout. This question 

 may be considered finally settled. I have had the advantage 



* Since this was written, Chem. elegantissima and the distinct Chem. 

 piisilla have occurred alive in tolerable abundance; they are largely 

 described. 



