BRITISH NEMERTEANS, AND SOME NEW BRITISH ANNELIDS. 421 



by a distinct cup or fold exteriorly. The anal nipple, moreover, is roughened by 

 small papillae. The bristles are slightly winged below the tip, and under a power of 

 700 diameters show minute serrations at the margins of the wings. Instead of 

 hooks, the first bristle-bearing segment has three very stout spines gently 

 curved at the tip, and the second and third four of the same character. They 

 have a distinct shoulder, and the chitinous substance is strongly striated longi- 

 tudinally. Only a small portion of the tip is usually seen beyond the skin. The 

 hooks in the segments which immediately follow have the processes above the 

 great tooth somewhat fewer (four to five), but the rest have six; and in those of 

 the last row, in front of the anal funnel, the denticles are even more numerous 

 towards the crown. The great tooth comes off somewhat stiffly at the base, and 

 its upper curve is not sinuous. Dr Malmgren does not notice the peculiar spines 

 anteriorly, but simply mentions that the hooks are fewer in those segments, and 

 omits several characteristics described above. There are no hooks on the soft 

 lobulated processes which succeed the last bristle-bearing segment, with its con- 

 spicuous transverse pad. The frontal lobes form two very prominent laminae. 



Another species, the Praxilla prcetermissa, Malmgren,* is not uncommon on 

 our western and northern coasts, inhabiting sandy mud at a depth varying from 

 four to eight fathoms. In a large specimen the teeth of the anal funnel are 27 

 in number. The hooks are characteristic, having about six teeth above the 

 large fang, and a well-marked interval between the latter and the origin of the 

 spinous tufts. The first three segments have simple and strong spines with the 

 apex slightly curved. There are also a few shallow crenations on the margins of 

 the cephalic lobes. A somewhat rarer species is Praxilla gracilis, SARs,f two 

 specimens of which appeared in the rich collection brought by Mr Jeffreys 

 from the Shetlands. The hooks of the first three bristled segments differ from 

 the others, and are spines with the apices more curved than in Axiothea, so as 

 to resemble a hook furnished with the large fang only. A third species of 

 Praxilla from the same region (North Unst, St Magnus Bay, and the Outer 

 Haaf), while agreeing in several particulars with P. pi'cetermissa, has its funnel- 

 teeth much more filiform and distinct — in one instance 14 in number. The hooks 

 (Plate XVI. fig. 13) have the large fang short and powerful, with the spinous 

 filaments arising close underneath, and a numerous array (seven to eight) of 

 diminishing teeth superiorly, the whole forming a very elevated crown, indeed it is 

 the most elevated of the series in this respect. The curves of the hook, especially 

 the posterior, are characteristic. The bristles are also peculiar, for instead of the 

 usual winged margin, the whole shaft is flattened out towards the translucent 

 tip, very minutely serrated at the edges, and tapered to a delicate point. The 

 shaft below the flattened portion is, as usual, finely striated longitudinally. 



* Nordiska Hafs-Annulater, p. 191. t Fauna litt. Norveg. ii. p. 15, tab. 2, figs. 18-22. 



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