347 
N. Arts. (Ehr.) Hare — Hunstanton saiuls. 
N. bohemica. (Ehr.) Rare — in the Breydon ditches. 
N. sculpt a. (Ehr.) This species is probably only a variety of the 
preceding ; it is somewhat more frequent but not plentiful. 
Breydon ditches. 
N. elegans. (Sm.) Nearly pure in a Yarmouth gathering; Brey- 
don and Wells — rare. 
N. (Pinn.) peregrina. (Sm.) Common in most brackish- water 
ditches. 
N. crucicula. (Sm.) Breydon, Wells, Lynn. 
N. subsalina. (Donk.) Frequent in all brackish-water localities. 
N. (Pinn.) radiosa. (Sm.) Common in all fresh-water ditches 
and streams. 
N. hennedyii. (Sm.) Very rare — in one of the Breydon gather- 
ings. 
N. inflata. (Sm.) Whissonsett, Flordon, Cossey, Holt, 
Ormesby; this occurs, although sparingly, in all fresh-water 
localities. 
N. gibberula. (Sm.) Parish drain, Ormesby ; the broad, Hick- 
ling ; Whissonsett. 
N. l.evissima. (Sm.) In most of the Ormesby gatherings, but 
not frequent. 
N. amphisbjekta. Bory. This species is present in all fresh-water 
gatherings. 
N. serians. (Kiitz.) Nearly pure in a small pond on Edgelield 
Heath ; more or less common in all fresh-water ditches. 
N. rhomboides. (Ehr.) Edgefield, Whissonsett, Ormesby, Flor- 
don ; this is not a common species in this county. 
N. crassinervia. (Breb.) Sparingly mixed with the above. 
N. cuspidata. (Kiitz.) Whissonsett, Ormesby, Holt; not fre- 
quent ; it also occurs in one of the Breydon ditches in 
which there is a considerable influx of fresh water in this 
habitat. The outline of the valve slightly differs from that 
of the type form, the sides being slightly rounded. 
N. ambigua. (Ehr.) Occurs in the same localities as the preced- 
ing species but is less frequent. 
N. rynchocepiiala. (Kiitz.) Flordon, Whissonsett ; common in 
most fresh-water streams. 
