120 ME. G. S. BRADY ON THE CEUSTACEAN FAUNA OF THE 



Fig. 4. Section of the upper portion of the tooth of Polypterus, from 

 Agassiz, showing the cap of enamel, a. 



Fig. 5 Section of portion of maxilla of HMzodopsis, much enlarged, ex- 

 hibiting the bony pillars supporting the teeth ; a a, bony pillars ; 

 b b. teeth in an abraded condition, the enamel having all disap- 

 peared, and, in some instances, portions of the dentine. 



V. — On the Crustacecm Fauna of the S alt-Marshes of Northum- 

 berland and Dm-hain. By George S. Brady, C.M.Z.S., &c. 

 (Plates IV., V.) 



At the Newcastle Meeting of the British Association, in 1863, I 

 read a short paper " On the Zoology of Hylton Dene,"* in which 

 was recorded the occurrence of vai'ious Entomostraca, Foramin- 

 ifera, and other Invertebrata, in slightly brackish water in the 

 neighbourhood of Sunderland. The subject appeared to me to 

 be one of very great interest, not only as exhibiting the man- 

 ner and degree in which the various denizens of fresh and salt 

 water are able to accommodate themselves to altered conditions, 

 as in the case of the common shrimp and stickleback, but also as 

 affording an opportunity for the study of a group of animals 

 which seem to be inhabitants exclusively of brackish water, and 

 which may be supposed to be modifications of species originally 

 dwelling in the sea, or perhaps in purely fresh water. Further- 

 more, the investigation of the inhabitants of our salt-marshes 

 might be expected to throw some light on the real character of 

 those Carboniferous and post-tertiary deposits which are sup- 

 posed to have been formed in estuaries, or lagoons of brackish 

 water. I have, therefore, during the last three or four years, 

 taken advantage of every opportunity that has come in my way 

 to collect microzoa — especially Entromostraca and Foraminifera 

 — from the salt-marshes of our district ; and I do not know of 

 any such locality in Northumberland or Durham which I have 

 not more or less thoroughly examined. The marshes which I 

 have visited are the following : — Cov/pen Marsh at the mouth of 

 the Tees, Hartlepool Slake, Hylton Dene and Claxheugh on the 



* See " Transactions of Tyneside Naturalists' Field Club," Vol. VI., p. 95. 



