200 



outwards, the 2 setae of the outer edge rather slender and remote from the apex. 

 Anterior antennae much shorter than the cephalic segment and rather thick at the 

 base, terminal part not attaining the length of the proximal one. Posterior an- 

 tennae with the outer ramus exceeding half the length of the terminal joint and 

 uni articulate. 1st pair of legs with the inner ramus distinctly 3-articulate and 

 somewhat longer than the outer, 1st joint much shorter than the other 2 com- 

 bined. Natatory legs rather strongly built, with the first 2 joints of the outer 

 ramus considerably thickened and densely spinulose, spines of outer edge very 

 coarse. Last pair of legs rather large, with very long and slender marginal setae, 

 distal joint narrow oblong, tapered towards the end and fringed with 5 setae, 

 inner expansion of proximal joint narrow linguiform, extending somewhat beyond 

 the middle of the distal joint, marginal setae 6 in number. 



Male considerably smaller than female and of more slender form of body. 

 Caudal rami rather unlike those in female and of quite normal appearance. Legs 

 of 3rd pair with the spine of the middle joint of the outer ramus exceedingly 

 strong and deflexed ; inner ramus 3-articulate, with the middle joint produced 

 inside to a slender deflexed stylet, last joint oblong oval in form, tipped with 2 

 unequal setae. Last pair of legs rather small, with the inner expansion of prox- 

 imal joint very slight and only provided with 2 denticulated spines. 



Colour whitish grey. 



Length of adult female 0.62 mm. 



Remarks. This form was described (but not figured) by the present au- 

 thor as early as the year 1862 as a species of the genus Canthocamptus. It was 

 subsequently observed by Prof. Brady, who regarded it as new, and described it 

 in his well-known Monograph as the type of the genus Attheyella, under the name 

 of A. spinosa. The form recorded by the same author at a later date as Para- 

 tachidius inermis, I am unable to distinguish from the present species. The 

 peculiar shape of the caudal rami in the female will suffice at once to distin- 

 guish this species from any of the other forms of Attheyella. 



Occurrence. I have only met with this form in larger lakes, on a muddy 

 bottom at a depth of some few fathoms. It was first observed in two lakes near 

 Christiania, Sognsvand and Maridalsvand, and I have subsequently also found it 

 in our largest lake, Mjosen, as also in some other lakes in the southern part of 

 the 'country. It moves rather slowly, and more frequently keeps to the bottom, 

 twisting its very flexible body between the loose mud. into which it is also en- 

 abled to bury itself with great dexterity. 



Distribution. Sweden (Lilljeborg), British Isles (Brady), Germany (Schmeil), 

 Holland (v. Breemen). 



