174 THE FRESH-WATER ALGAE OF ESSEX.
C. margaritiferum, Turp. Cooke, Desm., t. 39, f. 2. In
ponds, Wood Street, Walthamstow (Q.M.C.).
C. botrytis, Men. Cooke, Desm., t. 39, f. 4. In pools, High
Beach (A.H.H.) ; Snaresbrook.
Xanthidium armatum, Breb. Cooke, Desm., t. 45, f. 1.
In ponds, High Beach (A.H.H.).
Arthrodesmus octocornis, Ehr. Cooke, Desm., t. 47, f. 2.
In ponds, Snaresbrook.
A. incus, Hass. Cooke, Desm., t. 47, f. 4. In ponds, Snares-
brook.
A. convergens, Ehr. Cooke, Desm., t. 47, f. 1. In ponds,
Chingford ; Snaresbrook.
Staurastrum dejectum, Breb. Cooke, Desm., t. 49, f. 1.
In ponds, Snaresbrook.
S. cuspidatum, Breb. Cooke, Desm., t. 49, f. 5. In ponds,
Snaresbrook.
S. orbiculare, Ralfs. Cooke, Desm., t. 51, f. 7. In ponds,
Loughton.
S. muricatum, Breb. Cooke, Desm., t. 54, f. 5. In pools,
High Beach.
S. punctulatum, Breb. Cooke, Desm., t. 54, f. 6. In ponds,
Chingford; Snaresbrook.
S. alternans, Breb. Cooke, Desm., t. 54, f. 7. In ponds,
Snaresbrook; High Beach (A.H.H.).
S. polymorphum, Breb. Cooke, Desm., t. 58, f. 4. In
ponds, Chingford.
S. arachne, Ralfs. Cooke, Desm,, t. 63, f. 4. In ponds,
Snaresbrook.
ZYGNEMACEAE.
Zygnema cruciatum, Vauch. Cooke, t. 30, f. r. In ditches,
Snaresbrook ; High Beach.
Z. vaucherii v. stagnale, Hass. Cooke, t. 30, f. 5. In
pools, High Beach.
Z. anomalum, Hass. Cooke, t. 31, f. 1. In pools. High
Beach (A.H.H.); Easthorpe (E.G.V.). Var. lutescens, Hass. In
pools, West Bergholt Heath (E.G.V.).
Spirogyra crassa, Kutz. Cooke, t. 32, f. 1. In pools,
Colne (E.G.V.).
S. nitida, Dill. Cooke, t. 33, f. 1. In ponds, Kelvedon
(E.G.V.); Snaresbrook.