Phytoplankton of the River Thames. 643 
in the backwater, as contrasted with their occurrence in the 
main river, is also of interest. 
A little below Walton Bridge on the opposite (Middlesex) 
side of the river there is a short, very narrow backwater, 
which, perhaps owing to its origin in a small bay, formed 
(iii) Backwaters at Walton (July 1, 1903). 
The ‘ Sale ’ at 
Walton Bridge ; 
t = 23 °C. 
Backwater a 
little lower down; 
t = 2i- 5 °C. 
Main river at 
Walton ; t = 
2i-5°C. 
Stephanodiscus Hantzschianus, Grun. . . . 
rc. 
rc. 
rc. 
Melosira moniliformis (Mull.), Ag 
r. 
— 
r. 
„ varians , Ag 
c. 
a. 
rc. 
Campy lodiscus noricus , Ehrb 
— 
— 
r. 
Surirella biseriata , Br^b 
— 
— 
r. 
„ ovalis, Breb 
— 
r. 
rr. 
„ splendida , Ehrb 
r. 
— 
rr. 
Cymbella gastroides , Ktz 
— 
— 
Fragilaria virescens, Ralfs 
rc. 
c. 
rr. 
Synedra Acus , Ktz 
rc. 
rc. 
c. 
„ Ulna , Ehrb 
rc. 
rc. 
c. 
Nitzschia sigmoidea (Nitzsch), Sm 
r. 
— 
— 
Pleurosigma attenuatum (Ktz.), Sm. . . . 
vr. 
— 
vr. 
Pleurostaurum acutum (Sm.), Rabenh. . . 
rc. 
— 
— 
Scenedesmus quadricauda (Turp.), Br^b. . . 
rr. 
— 
r. 
,, acutus, Meyen 
r. 
— 
vr. 
Pediastrum Boryanum (Turp.), Men. . . . 
rr. 
— 
r. 
,, pertusum , Ktz 
rc. 
r. 
rc. 
,, pertusum, var. clathratum, Braun 
rc. 
r. 
rc. 
Eudorina elegans, Ehrb 
rc. 
— 
— 
Gonium pectorale , Mull 
— 
r. 
r. 
Pandorina morum , Ehrb 
rc. 
r. 
r. 
Richteriella polychaete , Fritsch. n. sp. 1 . . . 
r. 
— 
— 
Closterium moniliferum (Bory), Ehrb. 
r. 
— 
— 
„ Cornu , Ehrb 
r. 
— 
„ acerosu?n (Schranck), Ehrenbg. 
vr. 
— 
— 
Staurastrum paradox urn, Meyen 
rr. 
— 
— 
Ceratium cornutmn , Clap, et Lachm. . . 
vr. 
— 
— 
Synura Volvox , Ehrb 
c. 
r. 
— 
Dinobryon sertularia , Ehrb 
rc. 
— 
— 
Phacus longicaudus , Dujard 
r. 
— ■ 
— 
1 This new species is very closely related to Richteriella botryoides, Lemm., the 
only well-marked difference lying in the occurrence of numerous hyaline processes 
on each cell of the colony ; further investigation may show such differences to only 
warrant the establishment of a variety. Figures and full description will be given 
in a later publication. 
