George: New British Water Mites. 



215 



plant, each chamber at first openhig^ by a small pore, but later 

 becomini;- closed. Whether or not this association of Nostoc with 

 the liverwort can be regarded as a case of symbiosis, there seems 

 to be little doubt that a relationship of this kind exists in those 

 Hepaticae whose tissues contain a mycorhiza-like zone of cells 

 containing- the hypha^ of a fungus. 



NEW BRITISH WATER MITES. 



C. F. GEORGE, M.R.C.S., 

 Kirlon-in-Lindsey., lAncolnshire. 



Arrhenurus pyriformis n. sp. This very singular-looking- 

 mite was found at Manton, near Kirton-in-Lindsey, 20th 

 August 1902. It differs greatly in general contour from any 

 other male Arrhenurus I have yet seen ; indeed at first sight 

 it looks more like a female than a male, differing, however, 

 in having the anterior wider than the posterior, whilst in oval 

 females the posterior is 

 widest and roundest ; 

 besides this, the pre- 

 sence of the conspicu- 

 ous process, or spur, 

 on the fourth joint of 

 the last leg, which is 

 only found in the male 

 sex of Arrhenurus, at 

 once settles the ques- 

 tion. In colour it much 

 resembles the female 

 A. caudatus, being 

 blue, with an oval por- 

 tion on the anterior 

 part of the dorsum, 

 reddish brown, and 

 more diaphanous than 

 the rest part of the 

 chitinous skin of the 

 body. One remarkable circumstance not common in the male 

 Arrhenurus is the fact that the depressed oval line on the back 

 is complete posteriorly as well as in front. The perforated 

 plates on each side of the genital opening are well shown in 

 Mr. Soar's figure. The female is at present unknown. 



1903 June I. 



Arrhenurus pyriformis n.sp. (i) Dorsal, (p) 

 ventral surface of male, (3) last leg showing spur on 

 fourth joint. 



