DIATOMACEA. 39 
form. In a pure gathering of Navicula ambigua 1 found it 
sparingly scattered, three or four valves on each slide. On 
comparing the external forms they appear to me to be almost 
identical, and the fine strie of the Navicule are much the same 
as those in craticula. 
Faminy V. —SURIRELLEA—con. 
No. NAME. LocatLity. OccuRRENCE. 
ee 
Camprxopisets, Ehr. 
38 bicostatus, Sm. ....| Mostyn .sssseecesseevers July ’75....vr 
53 costatuS ....s+++e+| Rhydymwyn..-.sseeeeeee Sept. ’74.....1 
38 CTIDTOSUS .. eeeeceee| Mostyn ..seesseeeeeeers July ’75....vr 
1 spiralis ...6e eeeees Heron Bridge ......++++-| April’71....¢ 
PM sieeude. se 
The persistence with which some species occupy the same 
position is well seen in spiralis. Year after year I have found 
this form on the Heron Bridge Rock, sometimes in abundance, 
but never wholly absent. 
FAMILY VI.—STRIATELLEZ. 
Trrracycius, Ralfs. 
17 lacustre, Ralfs......| Cwm Bychan deposit ....| eccseseeeee VI 
TABELLARIA, Ehr. 
24 fenestrata, Kutz.....| Combermere ...+eeseeees March ’73 ....F 
24 flocculosa, Kutz.....| Combermere ...+++++rers March ’73..vc 
SrRIATELLA, Kutz. NOT REPRESENTED. 
Ruapponema, Kutz. 
52 arcuatum, Kutz. ....| Holywell .sssseseereess Sept. ’73....vr 
19 minutum ....-.---| HilbreIsland...seesesees July ’72....vr 
GramMMATOPHORA, Ehr. 
30 marina, Kttz....s0+| COlWYT seceseeseeeesrers July ’74 .056¥ 
Ron ee EE — eee 
FAMILY VII.—MELOSIREZ. 
Se SS 
CycLorELLa, Kutz. ‘ : 
3 antiqua, 7%. SP. «+++ Queen’s Park . ....+....| May’71....vr 
3 Kutzingiana, Thw..| Queen’s Park ..sseceseeee| May 71..+.--€ 
2 operculata, Kutz. .. Flookersbrook ...+++++++| May ’71....+.¢ 
24 rotula, Kutz ....... | Combermere sssseeee vere March ’73..vr 
21 Scotica, Kutz....e++| Mostyn secesseeeeeeeees July '72 2066 
Hyatoviscus, Ehr. 
14 levis, Ehr. ...+++++| Connah’s Quay..++sesees May ’72....vr 
he be eee 
