221 



two years. M. alboluhris appears to mature in llie same periofl. In 

 every specimen I find on the body vvhoi-ls, about one whorl from the 

 aperture, lines of growth thicker or darker than the i-est, and about 

 two and a half whorls from the apex a secc)nd and fainter series of dark 

 lines. Besides these hibernation marks there are other irregularities less 

 prominent, which indicate diy periods in summer, when the animal was 

 obliged to remain inactive and growth was retarded. When the sign 

 of hibernation in the boily whorl is preceded, as it sometimes is, at a dis- 

 tance of four or five millimeters by a mark less distinct, it may be 

 inferred that the autumn of the second year of the shell's life was cold 

 and that the animal went early into winter quarters, but fine weather 

 following, it came forth again and was able to grow a little before the 

 cold came to stay. 



Although the iresodons attain their full size in two years, the 

 shell at the end of that time is quite thin. The occrreuce of thick and 

 thin shells in the same locality is due to the fact that some are old and 

 others young. 



Vallonia puldiella, MdJler. — This is another of the helices found 

 here which has a distribution both in America and Europe. It is also 

 said, like C. fulcus, to inhabit Siberia and the Azores, and has accord- 

 ingly not only a circumpolar range in three continents, but extends well 

 to the south in a fourth. It is one of the smallest of helice.s, measur- 

 ing only from 2 to 2 5 mm. in diameter. Although so Sinall, its pe;u-ly 

 whiteness renders it easily discernalde, and it may be found in quan- 

 tity almost anywhere here, under logs and stones near springs or the 

 margins of streams. It manifests an especial preference for wet sta- 

 tions and is moie common by far in open fields than in the woods. 

 The animal is milk white in color, in part tinged with yellow, auM is 

 very timid. The slightest jar or movement made neu* by causes it to 

 withdraw within its shell. The observer wlio places it on a slide and 

 awaits its exit needs to be the pos.sessor of great patience, but he will 

 not be unrewarded for his pains though the little linhitant refuses to 

 come forth. The shell itself is a beautiful object under the microscope, 

 and is sufiiciently transparent to permit the beating of the animal's 

 heart to be distinctly seen within it. 



Puctum minutissimum, Lea. — 1 his is one of the smallest land 

 shells known, and if, as some think, identical with /'. 'py(jinceui)i. of 



