8 



TETRERBS MTTRATA. 



bevelled divisions. Each of these lobes is a massive process which tapers in lateral view 

 anteriorly, has a twisted sulcus dor sally, and the firm margins of which have the slender 

 palese. Externally is a row of tapered papillae, as in other forms, which, commencing on 

 the edge behind the palese, cease at the rounded anterior end of the lobe. The external 

 palese (Plate CXXIII, figs. 1 and V) form a single row of spatulate bristles which follow 

 the curve of the margin, and are slender posteriorly, stronger in front. Moreover, the 

 posterior bristles slope upward and forward, whereas the anterior are nearly proclivous. 

 Each of the posterior bristles starts from a rounded sac at the base, is much tapered, then 

 gradually dilates into a broad, flattened, translucent blade, after which it diminishes to 

 the finely-pointed tip (Plate CXXIII, fig. 1 a). The anterior bristles are larger, and, as 

 mentioned, they project nearly horizontally when the animal lies flat in a vessel. These 

 join the still more powerful anterior series of the inner row, which, in some cases, 

 extend boldly from the inner half of the anterior curve. The anterior end of the inner 



Fig. 137 a. — Diagram of the anterior region of Tetreres murata. p., palps ; cil.c, ciliated channel formed of 

 membrane ; ext., external border ; int., internal border ; sep., separation from the prostomium pr. ; per., peri- 

 stomium (lower lip) . After Arnold Watson. 



row of paleas has the strong bristles just mentioned which present stout and not very 

 acute points (Plate CXXIII, fig. 1 /; and 1 //). When fractured long fibres hang from 

 the interior. These powerful bristles project considerably from the surface, but behind 

 the anterior edge the rest of them are deeply imbedded in the tissues, only the tip being 

 visible. All are directed obliquely forward and slightly upward. Attached to these is 

 a minute Campanularian with a ringed stalk, a comparatively large theca and a thick 

 rhizome. Next these powerful bristles are less robust forms with a tapered base, flattened 

 and pointed tip. Those deeply inserted in the tissues behind have the thickened chitinous 

 tips of the larger forms in front, whilst their hold of the tissues will enable them to act 

 as levers or protective organs. The base has a rim and abuts also on the rounded mass 

 seen in the outer posterior paleas. 



Opposite the last and larger external papilla of the coronal row is, beneath the crest 

 of the ridge on each side, a strong, sharp, dark brown, curved hook which is guarded by 

 the flaps of a conical, fleshy papilla. The point of the hook in the preparations is directed 

 inward, but it probably can be moved in various directions. The long straight bristles 



