SALT-MAESHES OF NORTHUMBERLAND AND DURHAM. 123 



The Copepoda whiich I have found in brackish water are as 

 follows : — Dias longiremis, Lilljeborg, Temora velox, Lilljeborg, 

 Cyclops cequoreus, Fischer, C. Lubbockii, n. sp., Dactylopu^ tis- 

 hoicles, Clans, Delavalia jyalustris, n. gen., Tachidius hrevicornis, 

 Lilljeborg, and two species of Cleta, which I have not yet been 

 able to work out satisfactorily. 



Temora velox appears to be the most abundant of these species, 

 occurring in great profusion in almost all brackish pools on our 

 coast, more especially in the autumn months. I have only once 

 met with it in the open sea. 



At Seaton Sluice a little mite, Halacarus rliodostigma, Gosse, 

 occurred pretty plentifully. I did not notice it while alive, and 

 can therefore give no account of its habits. The pools at Seaton 

 Sluice have afforded me a decidedly greater variety of Entomos- 

 traca than any other similar locality, and I am disposed to attri- 

 bute this, in part, to the greater abundance of algae which they 

 contain. Vaucheria velutina and Conferva linum form the prin- 

 cipal vegetation, and certainly harbour a great number of these 

 microzoa, but many species are found very abundantly where 

 there is scarcely any vegetation, as for instance Temora velox 

 and the three species of Ostracoda previously mentioned. Cy- 

 theridea littoralis and the Foraminifera seem to haunt the mud 

 exclusively, and are not to be taken in any quantity, merely by 

 sweeping the weeds, and I am disposed to think that the genus 

 Cleta has the same habit. 



I am at a loss to account for the constant existence in salt- 

 marshes, of their characteristic pools. They are quite unlike any 

 other pools, being mostly shallow (about six or eight inches in 

 depth), the bottoms perfectly flat, and the sides perpendicular, 

 as if cleanly punched out of the ground, never shelving or saucer- 

 shaped. Wherever a salt-marsh exists pools of this kind are 

 sure to be found, but the mode of their formation is to me a 

 mystery. 



In the following notes on the species of Entomostraca I have 

 not thought it desirable to give descriptions or figures of any ex- 

 cept entirely new species, or species new to the British Fauna. 

 The rest have been sufficiently described elseAvhere. 



