14 Prof. M'Intosh's Notes from the 



exceed the figure mentioned. The body is widest in front 

 and gradually tapers behind the middle to the posterior end, 

 Avhere the rounded anus is terminal. The dorsal surface is 

 moi'e or less rounded, the ventral flattened and marked by 

 the scutes from end to end. A slight depression occurs in 

 the mid-dorsal line anteriorly, and, continuing to the right 

 behind the sixth bristle-tuft, it crosses the seventh segment 

 obliquely to the middle line, whence it passes to the tip of 

 the tail — cutting the ventral scutes into two in each seg- 

 ment. Six bristled segments are present in the anterior 

 region and five uncinigerons rows, but occasionally only 

 five and four occur respectively. Other variations, ap- 

 parently arising from lost parts in process of reproduction, 

 show the ventral furrow running to the front or a diminished 

 number of anterior ventral scutes. Moreover, the two 

 anterior scutes may be split by a furrow — quite indepen- 

 dently of the main ventral furrow. The first setigerous 

 process is situated behind the collar, and is inconspicuous. 

 It has a small tuft of simple bristles with acutely tapered 

 tips and narrow wings, as in the dorsal group of the anterior 

 region. The bristles of the succeeding segments of the 

 anterior region (five in number) have dorsally translucent 

 bristles with straight shafts and finely tajiered tips with 

 narrow wings — the u})per having longer and more delicate 

 tips and the lower narrow spatulate forms ; the outline of 

 the wings is more or less a long ellipse, the tapering 

 shaft being continued as a fine process distally. Moreover, 

 those with broader tips form a shorter row than those witii 

 more elongated tips. The outline of the tip of the latter 

 bristles thus essentially differs from that in Potamilla re7ii~ 

 j'unnls and also from those of P. torelli. In the posterior 

 region the bristles form a tulip-like fascicle, Avith a knee or 

 curvature on each bristle toward the end of the shaft, the 

 convexity with the wnngs being external : those with the 

 longest and most delicate tips are dorsal, those with slightly 

 broader wings are ventral, and the former are most conspicuous 

 near the tip of the tail. In the anterior region five unciui- 

 gerous rows lie to the ventral edge of the setigerous processes, 

 their inner ends impinging on the scutes opposite them. 'I he 

 first commences opposite the second brisrle-tuft, and all are 

 longer than those of the posterior region. The hooks are 

 in a single row, with a main fang and a series of serrations 

 above it, a neck of moderate length with stria? where it 

 enlarges into the boldly convex prow, and an oblique 

 tapered base (corresponding to the shaft). Moreover, a 

 series of short modified bristles occurs with them, the tips 



