BARTSCH: NEW ENGLAND PYRAMIDELLIDAE. 
91 
Among the Pyramidellidae it seems to be the rule, that the most 
variable forms are the most abundant and most widely distributed. 
This leads one to wonder if it is not the optimum condition that 
weakens specific bonds and tends to throw an organism into the so 
called "state of flux" rather than the reverse. 
An extreme variety of this species, we will designate under the name 
senilis. 
We have examined the following specimens : — 
Cat. no. 
119 
120 
155 
761 
826 
844 
203,773 
203,774 
203,776 
1,106 
203,777 
602 
203,778 
766 
203,779 
829 
203,780 
851 
203,781 
858 
203,782 
203,783 
655 
203,784 
203,775 
203,785 
No. of 
spec. 
3 
1 
1 
1 
1 
1 
9 
30 
10 
50 
6 
16 
2 
4 
1 
1 
1 
2 
2 
2 
1 
2 
1 
1 
3 
1 
7 
16 
5 
U.S.F.C. Depth Temp. Disposition of 
sta. Locality. (fms.). material. 
Wood's Holl, Mass. Wood's Holl coll. 
203,786 6 
Branford, Conn. 
1623 Off Penfield Reef 10 
(Long Island Sound) 
1624 Off Penfield Reef 5f 
(Long Island Sound) 
U. S. nat. mus. 
H. W. Winkley coll. 
U. S. nat. mus. 
H. W. Winkley coll. 
U. S. nat. mus. 
Wood's Holl coll. 
U. S. nat. mus. 
Wood's Holl coll. 
U. S. nat. mus. 
Wood's Holl coll. 
U. S. nat. mus. 
Wood's Holl coll. 
U. S. nat. mus. 
Wood's Holl coll. 
U. S. nat. mus. 
Wood's Holl. coll. 
U. S. nat. mus. 
" ti (C 
Wood's Holl coll. 
U. S. nat. mus. 
II II II ' 
H. W. W'inkley coll. 
65° U. S. nat. mus. 
64° " 
