112 



0. D. SOAR ON A CONTRIBUTION' TO THE LIST OF 



smaller than the female, but tlie only difference in surface 

 structure is in the genital area. 



The palpus (Fig. 5), which is the most important feature., 

 readily distinguishes it from other species of the genus. In length 

 it measures about 0'35 mm. The segments taken separately 

 measure: first, 0'02mm. ; second, 0*10 mm.; third, 0'06 mm. i 

 fourth, 0*1 3 mm. ; and the fifth, 0"04 mm. The fourth segment 

 is the longest, and has a long thin hair about the middle of the 

 inner edge. This hair is about 0*06 mm. in length. 



From Lake Nyassa. (Tube No. 3.) 



Unionicula cunningtoni sp. nov. (PI. 5, Figs. 10-12.) 



This mite is very like Unionicula figurcdis Koch, but on closer 

 examination it is seen to be different in two or three material 

 points. The last segment of the palpus has three distinct teeth ^ 

 which take up nearly the whole of the segment (Fig. 12). In 

 U, JiguraUs the teeth are hardly perceptible. The acetabula are 

 five on each side of the genital opening two on the upper plate 

 and three on the lower. The three lower ones are placed near 

 the marginal line of the plate. In U. Jigurcdis the median 

 acetabulum is placed nearly in the centre of the plate. Exactly 

 behind the eyes is a long split seta (Fig. 10). I know of no other 

 mite having this distinguishing characteristic. The length of 

 the body of the female is about 1-10 mm. 



Complete List of Hydraciinids found in the East African 



Lakes 



(Including, as far as I have been able to ascertain, all those 

 previously recorded. The figures in brackets refer to the 

 bibliography. ) 



1. Unionicula crassipes Miill. Victoria Nyanza. (1, 5.) 

 horgerti Daday ,, (1? 5.) 



O. 



5> 



5? 



falc'ifer Daday 



j 



(1,5.) 



