THE AMERICAN NATURALIST. [Vol. XXXVII. 



walkers and climbers, walking with facility either forward or 

 backward. Lateral margins of posterior abdominal segments 

 produced into a point. 



Outer caudal setae fringed on both sides, habitually held at 

 an angle of 6o° to 70 (Fig. 2, e) ; length about 12 mm. ; joints 



over seventy, short at the base, becoming elongated toward 

 the tip ; margins of joints finely spined, hairy only at the 

 nodes (Fig. 2, d). 



Gills exposed, leaf-like, held laterally, on segments 1 to 7, 

 their movement comparatively slow (about 1 30 per minute) ; on 

 the first segment they are simple lanceolate rudiments, forked 

 for over two-thirds their length into two slender sparsely hairy 

 branches (Fig. 2, a) ; they are double on segments 2 to 7, ovate 



