The Arenicolidts of South Africa. 9 



by closely set oblique lines and has a finely dentate margin (Fig. 3). 

 The other margin of the seta, for a distance of 1'5 to T7 mm. from 

 the tip, bears numerous regularly arranged structures which, seen 

 under low or medium magnification, look like long fine teeth ; 

 similar structures are also present along the laminate side of the 

 seta for a short distance proximal to the lamina. In most species 

 of Arenicola the "teeth," corresponding to those just described, are 

 more closely pressed to the shaft of the seta, whereas in A. loveni 

 they project at an angle of 30 to 40 from the shaft, and are con- 

 sequently much more obvious, especially as in A. loveni they are 

 also of larger size. The exact nature of these outgrowths on the 

 shaft of the seta is difficult to determine, but, under an immersion 

 objective, it is seen that they are regularly arranged crests passing 

 round the shaft (Fig. 4). The apparently undivided base of the crest 

 is fixed to the shaft and its distal margin, that is its free edge, is 

 subdivided into a large number of fine teeth. Each crest appears to 

 be a comb-like structure, bent so as to envelop the greater portion 

 of the shaft of the seta, the curved portion being seen in profile 

 where it projects beyond the edge of the shaft. The regularly 

 arranged structures, seen under low power, as fine teeth along one 

 margin of the seta are, then, the profile view of these crests, which 

 remind one of the similar crests or " Sagebliitter " present on the 

 setae of some Aphroditidae and certain other Polychaeta. The 

 laminate portion of the seta bears on its surface numerous fine 

 processes the pointed tips of which are directed at slightly different 

 angles ; those seen in profile at the margin of the lamina form a 

 regular series of very fine teet'h, In each interval between the 

 " Sagebliitter " there is a denser transverse band, the presence 

 of which, at regular intervals of about 10 to 12^, gives to the distal 

 portion of the shaft of the seta a transversely striated appearance, 

 which is well seen even under low magnification (about 50) and 

 forms a very striking feature of the notopodial setas of A. loveni 

 (Fig. 3). Kinberg has clearly indicated the transverse striation 

 in his figure (lo, s.) of a seta. 



The well-marked striation and the high degree of development of 

 the crests are two 'characteristic features by which the notopodial 

 setae of this species may be readily distinguished from those of any 

 other species of Arenicola. 



Crotchets from the nineteenth neuropodium of the type specimen 

 are about '75 mm. long (Text-Fig. II., A). The distal end of the 

 crotchet does not bear teeth behind the rostrum, and there is a wide 

 angle about 130 between the rostrum and the shaft. Both these 



