30 CHARLES D. SOAR ON 



Oxus plantaris Sig Thor. 

 PL 1, figs. 1-13. 



1900. Oxus plantaris Sig Thor. Eine Neue Oxus-art, Nyt Mag, 

 Natur., xxxviii. pages 277-279, plate xi. figs. 10-12. 



1911. Oxus plantaris Halbert. Clare Island Survey, part 39^\ 

 page 25, plate ii. fig. 21, a-c. Proc. Roy. Irish Acad., 

 vol. xxxi. 



Female. — Length about 1'26 mm., breadth 0'80 mm., height 

 0-75 mm. Neither of the writers above mentioned gives the 

 measurement of this mite, but each says it resembles 0. ovalis; with 

 us 0. ovalis is much smaller. The shape is a long oval ; viewed 

 from the dorsal surface it is much like Frontipoda or Gnaphiscus, 

 but from the lateral view it will be seen to be very much 

 less arched (PI. 1, fig. 2). The colour in nearly all Mr. Harris's 

 specimens was a bright orange with black velvety-looking mark- 

 ings on the dorsal surface. The legs were also of the same bright 

 orange colour. There is a patch of light orange colour in the 

 centre of the dorsum. Mr. Halbert gives the colour of his female 

 as reddish-brown with slate- coloured appendages. The colora- 

 tion of the water-mites we know from experience does not count 

 for much, and there is no doubt it is regulated to a large extent 

 by the environment. There was one female in the collection 

 inclined to blue in the legs and another one (a male) with pale 

 bluish legs, orange- coloured at the distal end of each segment, 

 but they were very faintly coloured and had nothing of the 

 brilliancy found in the other specimens. The skin of the body 

 is soft and striated ; the dorsal surface has a number of dermal 

 glands and hair-pores, but these are hardly noticeable during 

 life on account of the brilliant colouring. The epimera are 

 thick and the surface is granulated. The eyes black and placed 

 well forward on the body about 0-20 mm. apart. The ventral 

 surface is more than half covered by the epimera (PI. 1, fig. 1). 

 At the apex of the first pair of epimera there are two strong 

 curved spines (PI. 1, fig. 3) which form one of the character- 

 istics of this species. The capitulum is small and does not 

 extend as far forward as the apex of the epimera. The palps 

 are about 0-23 mm, long (PI. 1, fig, 4). The second segment 

 has two short spines on the extensor margin and two long ones 



