!. 



about the length of the anal segment, and slightly divergent, outer edge smooth, 

 inner finely ciliated, tip obtusely rounded; apical setse of moderate size and 

 somewhat spreading, the innermost but one about equalling the tail in length. 

 Anterior antennae much shorter than the cephalic segment, and composed of 19 

 joints, terminal part bi-articulate. Posterior antennae with the penultimate joint 

 scarcely more than half as long as the preceding one; apical spine rather strong. 

 Oral cone comparatively small, extending only slightly beyond the insertions of 

 the anterior maxillipeds, and terminating in a sharp point apparently formed by 

 the extremity of the posterior lip. Masticatory part of mandibles cultriform, with 

 a very fine denticulation on the inner edge of the extremity. Maxillae with the 

 inner lobe somewhat curved and tapered distally, apical setae comparatively short; 

 outer lobe very narrow, linear, with the apical setae longer than those on the 

 inner lobe. Anterior maxillipeds rather powerful, with the claw very strong and 

 slightly curved at the end. Posterior maxillipeds of the usual structure. Natatory 

 legs differing a little in their armature from those in the preceding forms, the 

 terminal joint of the outer ramus being provided inside in 1st pair with 3, in 

 2nd pair with 5 set*; same joint of inner ramus in the last 2 pairs with only 

 a single spine on the tip. Last pair of legs with the distal joint rounded oval 

 in form, and armed on the hind edge with 2 blunt spines, the extremity car- 

 rying 2 setae accompanied inside by a small bristle. Ovisacs comparatively small, 

 rounded oval in form. 



Male, as usual, smaller than female, and having the anterior division 

 far less dilated. Tail with the segments still more sharply marked off from 

 each other; genital segment greatly swollen. Anterior antennae 17-articulate, 

 and each provided with about 7 supplementary sensory filaments curving 

 backwards. 



Body in both sexes generally of a brownish grey hue, with the anterior 

 antennae and natatory legs very dark-coloured, almost black; tail also partly 

 tinged with a dark brownish colour. 



Length of adult female amounting to 1 55 mm., of male to 1.20 mm. 



Remarks. This form was recorded as early as the year 1875 by Brady 

 & Robertson under the name of Cydopicera n\<ir'ii><'*. and was justly referred b} 

 Giesbrecht to the genus Dermatomyzon, as defined by Glaus. It seems however 

 very questionable to me, if Giesbrecht was right in identifying the form described 

 by Glaus under the name Dermatomyzon dei/tni* with the present species, as the 

 latter differs not only in its much larger size and peculiar coloration of the body, 

 but also in the presence on the male anterior antennae of greatly developed 



