TA THE NAUTILUS. 
lies everywhere our best chance of ascertaining the principles of 
evolution. 
The varieties of Helix nemoralis are classified according to the 
following principles: First, variation in the ground-color of the 
shell, with the name Jibe//u/a for yellow shells, rubella for pink shells, 
petiveria for pale brown or fawn-colored shells, etc. Secondly, 
variation in the banding, for which a band-formula is used. The 
typical shell has five bands, three above the periphery and two 
below, and its formula is accordingly 12545. If a band is missing, 
a 0 is placed in its stead—thus 12045 has the third band of the type 
missing, while 00000 is the formula for a bandless shell. If two 
or more bands are coalesced, they are bracketed together, thus, 
12(345). If a band is imperfectly developed, it is indicated as a 
small figure below the line, thus, 12,45. Ifa band is split into two, 
the number is repeated, as 1235(45), while an extra band which 
cannot he assigned to any of the usual five, is represented by an X, 
as 003X00. The formula should always be taken from near the 
mouth of the shell. These, then, are the ordinary kinds of varia- 
tion, while other unusual characters are expressed in suitable terms, 
as tenuis for a very thin variety, compressa for a depressed form, 
minor for asmall form, albolabiata for a white-lipped shell, etc. These 
terms are used in conjunction with one another, to indicate the differ- 
ent peculiarities of any given shell. The band-formulz express them- 
selves, and need not, as a rule, have the name of their author quoted 
afterthem. But in introducing these band-varieties to the American 
fauna, I have given the names of their first recorders, as a hint to their 
history in Europe. For certain of them, I have given special names 
bestowed by French authors—as brissonia for petiveria 12545. If 
these names are to be adopted, it will be necessary to bestow many 
new ones, as a large number of combinations have not come under 
the notice of the aforesaid authors, but to my mind it is more con- 
venient to use the band-formule in conjunction with the color- 
names. There is only one thing to be said for the names given to 
combinations, that if misprinted they can hardly lead to any real 
confusion, whereas band-formulz may be misprinted easily enough 
in such a way as to lead to erroneous records, which may never be 
corrected. ° 
All the shells of H. nemoralis I have seen from the colony at 
Lexington, Va., were collected by Prof. J. H. Morrison, and number 
altogether 103. The first consignment, sent me through Mr. H. A. 
