THK NAUTILUS. 39 



Amnicola limosa Say. Very variable and abundantly represented. 



Amnicola g alb ana Haldeman. Tliis characteristic fossil is very 

 abundant in the White Pond formation. It shows some variation 

 in the height of the spire, but seems to be easily separated from A. 

 limosa. Several monstrosities of galbana were found in this collec- 

 tion ; two were scalariform and the others (G) had the spire variously 

 contorted, like the forms of Planorbis complanatus figured by Euro- 

 pean conchologists. One specimen had the spire almost concealed 

 by the gibbous last whorl. Monstrosities seem to be rare, as only 

 eight were found in a lot of over two thousand specimens. 



Valvata tricarinata Say, var. confusa Walker. This is nearly as 

 abundant as the Amnicolas. Only a small percentage of the speci- 

 mens were typical confusa with two well-defined keels, the majority 

 having the basal keel strongly developed, the upper part of the whorl 

 being rounded. In some specimens the two keels are so strong that 

 they form elevated ridges. 



Physa ancillaria Say. Not uncommon. 



Aplexa hypnorum Linne. Two specimens of a small Aplexa which 

 seems referable to hypnorum are in the collection. 



Planorbis campanuJatus Say. Typical, but not abundant. 



Planorbis bicarinatits Say. Many specimens of this species show 

 a tendency to form spiral lines, similar to those on var. slriatus 

 Baker. 



Planorbis deflectus Say. Common and typical. 



Planorbis exacutus Say. But one specimen of this species was 

 found. 



Limnsea galbana Say. Not common. 



Limnsea humilis Say. Not common. 



Succinea retu?a Lea. Not common. 



ON CATALOGUING A COLLECTION OF SHELLS. 



BY MRS. M. BURTON WILLIAMSON. 



When I began to catalogue my shells I used a ledger blank book, 

 but in time the book looked untidy, as the space was not sufficient for 

 the addition of species new to the collection that from time to time 



