. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. 44 Arenicolidae absence of a lamina along the distal portion, and in the nature and comparative abundance of the processes present in that region of the chaeta. The most highly developed notopodial chaetae present in the genus are found in A. loveni. In the notopodia of this (and some other) species the chaetae seem to be in two more or less distinct series, an anterior and a posterior; the chaetae of the anterior are shorter than those of the posterior row, but they have the same form and structura
. Catalogue of the Chaetopoda in the British Museum (Natural History). Oligochaeta; Polychaeta. 44 Arenicolidae absence of a lamina along the distal portion, and in the nature and comparative abundance of the processes present in that region of the chaeta. The most highly developed notopodial chaetae present in the genus are found in A. loveni. In the notopodia of this (and some other) species the chaetae seem to be in two more or less distinct series, an anterior and a posterior; the chaetae of the anterior are shorter than those of the posterior row, but they have the same form and structural detail. The longer chaetae are about 6*6 to 6 • 8 mm. long, and the shorter ones 5'3 to 5*6 mm. Each has a moderately uniform diameter for the greater part of its length, but in its distal portion tapers to a fine point. For a distance of 1 to 1*3 mm. behind the tip, there is, along one edge of the chaeta, a well-marked lamina (Fig. 11 a), which attains a breadth of 15 yu. and, as seen under medium magnification, is marked by closely set oblique lines and has a finely dentate margin. The opposite edge of the chaeta bears numerous regularly arranged processes, which, under low or medium magnification, appear as fine teeth projecting at an angle of about 30° to 40° from the shaft of the chaeta, but which, examined with an immersion lens, are seen to be crests passing round the shaft (Fig. 11 b). The undivided base of each crest is fixed to the shaft, and the distal por- tion of the crest, that is, its free margin, 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 part of the shaft of the chaeta, the curved por- tion of the crest being seen in profile where it projects from the shaft. The regu- larly ari'anged structures visible, under low power, as fine teeth along one margin of the chaeta are, then, the crests seen in profile, and. 'ig. 11.—A. loveni. A, Distal third of a notopodial chaeta,
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