C. D. SOAR OX THE GENUS HYDRACHNA. 281 



Norfolk Broads. Named in honour of Mr. Williamson, of 

 Edinburgh, well known as a writer on the North British 

 Hydrachnidae. 



20. Hydrachna fuscata, n.s. 



Female 24 mm., male 2*1 mm. in length. A very dark- 

 coloured mite, appearing, when examined in water, almost black. 

 The legs are red, marked with yellow at the joints. The skin 

 is covered with fine rounded papillae. The genital area of the 

 female has a very deep inbaying from the anterior margin. 

 The male genital area is only very slightly curved inwards. 

 The small chitinous plates or muscle attachments are close 

 behind the eyes, but are placed a little nearer the median line 

 than in 11. incisa or //. haJherti. This mite has been found in 

 Lincolnshire, Shropshire, and Hertfordshire (Fig. 23). 



21. Hydrachna incisa, Halb. 



A very dark-coloured mite first described in 1903 by Mr, 

 Halbert, by whom it was found in a pond near Carrigaline, 

 County Cork, Ireland, in 1900 (Fig. 22). 



It was my intention in this paper to give a list of localities 

 where these mites have been found, on a scheme suggested to 

 me by Mr. Balfour Browne, in which the British Isles are 

 divided into counties and vice-counties, the divisions being 

 numbered for convenience of reference and for the economising 

 of space. Unfortunately, however, many of the gentlemen who 

 have so kindly sent me specimens for examination in the 

 preparation of this paper have omitted to supply me with 

 sufficient data for the purposes of such a list. I am, however, 

 gradually acquiring the necessary information, and hope to 

 publish later a full detailed list on the lines suggested 

 above. 



I wish to thank the following gentlemen for the loan of 

 specimens and mounted slides for the preparation of this paper : 

 Mr. Halbert, of Dublin ; Mr. Williamson and Mr. Evans, of 



