LEANDER LONGIROSTRIS AND OTHER BRITISH PRAWNS. 97 



9. Some Notes on Leander longirostr'is M. Edwards, and 

 other British Prawns. By Robert Gurney, M.A., 

 F.L.S., F.Z.S. 



[Received November 18, 1922 : Bead February 20, 1923.] 



(Text-figures 1-6.) 



Contents. 



Page 



Introduction 97 



Characters of British Prawus 98 



Leander serratus 99 



„ squilla 102 



„ adspersus 106 



„ longirostris 108 



„ „ (moulting) 113 



FalcBmonetes va7'ians 114 



Modification of Pleopods for Egg-bearing 120 



Falcemonetes varians var. mesogenitor 121 



The European Prawns of the genus Leander have been very 

 thoroughly revised by De Man *, who has shown that L. longi- 

 rostris occurs commonly on the Dutch coasts, where it has hitherto 

 been recorded under the name of L. squilla. The two species 

 closely resemble one another in respect of the form of the rostrum, 

 but differ greatly in other respects, and De Man's very careful 

 and detailed description has made discrimination of the species 

 an easy matter. 



In Norfolk a prawn has long been known to occur in the 

 lower reaches of the rivers flowing into Breydon Water, and has 

 been recorded by Mr. A. H. Patterson f and myself + under the 

 name of L. squilla. Having obtained a number of specimens of 

 this prawn from Breydon Water in June 1921, a careful examina- 

 tion of these specimens was made, with the result that it became 

 perfectly clear that they could not be referred to any species 

 hitherto recorded as British. Subsequent reference to De Man's 

 paper at once proved them to belong to Leander longirostris 

 M. Edw. An examination of old material and of specimens 

 since collected in the Norfolk rivers and at various points on the 

 coast has shown that L. squilla does not normally occur at all in 

 any part of the rivers, but that it is quite common between tide- 

 marks on the coast. 



I have also visited the estuaries of the East Coast from Norfolk 

 to the Thames, and have not been able to obtain any evidence of 

 the occurrence of L. longirostris anywhere except in Breydon * 

 Water and the rivers entering it. 



* De Man, Tijdschr. Nederl. Dierlc. Vereen. (2) xiv. p. 115 (1915-16). 



t Zoologist, (4) ii. p. 178 (1898). 



X Trans. Norf. & Nor. Nat. Soc. vii. p. 637 (1904). 



Proc. Zool. Soc— 1923, No. YII. 7 



