40 



J. Stephenson: The Fauna of Brackish Ponds. [Vol. II, 



consists of the tenth and perhaps the ninth segment also. In 

 the anterior part of the body the segments may be dehmited on 

 the ventral surface by a series of narrow, groove-like, transverse 

 markings. 



There are two dorsal and two ventral setal bundles in all 

 segments from the second onwards. The setae are of two kinds, 

 hook-setse and needle-setae ; the most anterior bundles, both dorsal 

 and ventral, consisting of needle-setse, the posterior of hook-setse. 



The needle-setae are from "oS to "12 mm. in length, finely 

 pointed, not bifid, the extreme point being slightly recurved. 

 They are somewhat bayonet-shaped, and appear to be definitely 

 strengthened or thickened along the convexit}^ of the angle of their 

 chief curve (v. text-fig. 2). They project from the bod^^-wall for 

 about half their length, that is, from the region of the angle ; the 

 angle looks forwards, and the distal pointed extremity backwards 



Fig. 2. 



Fig. 



Fig. 2. — A needle-seta : a.. Apparent ridge-like thickening of needle-seta at 

 its most prominent angle. 



Fig. 3. — A hook-seta: fo., the slightly thicker part of the hook-seta, near its 

 free end. 



The hook-setae are from •033 to -055 mm. in length. In the 

 most anterior segments (vi — viii) in which they occur, they are 

 longer (-05 — -055 mm.) than is the case posteriorly (mostly "035 

 — -04 mm.). They are bifid at the free end ; the proximal prong 

 of the fork is considerably longer and stouter than the distal, and 

 its axis is about at right angles to the shaft of the seta. There 



