THE FALSE-SCORPIONS OF SCOTLAND 



i6i 



(Z^? ^^ cofttinued.) 



HYDRACHNIDS FROM THE ISLAND OF TIREE. 



By Wm. Williamson. 



During a few days' stay in the Island of Tiree in August 

 1907, I obtained some specimens of Hydrachnids in the 

 neighbourhood of Scarnish. The collection embraced only 

 three species, of which two, Thyas lofigirostris^ Piersig, and 

 TipJiys liliaceus, M tiller, have not been recorded before for 

 Scotland. 



Thyas longirostj'is, Piersig. — This species was briefly 

 described by Piersig in 1895 i" the " Zoologischer Anzeiger; " 

 a more complete description is given in his work on the 

 German Hydrachnidae — " Zoologica," Heft 22, 1897- 1900. 

 T. longirostris^ Piersig, may be recognised by the shape of 

 the piece of chitin which accompanies the unpaired median 

 eye. In the species already recorded as occurring in 

 Scotland, viz. T. venusta, Koch, and T. extendens, George, 

 the chitin takes the form of a small ring in the centre of 

 which the median eye is placed. In T. longirostris, however, 

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