Gaily ilfan'ne Lahoratory, St. Andrews, 35 



setigerous segment as a low elevation with a short row of 

 hooks, which in outline differ from the typical forms in 

 the middle of the hodj', insofar as the base is shorter and 

 proportionally thicker, and a considerable elevation occurs 

 on the anterior outline beneath the main fang. The typical 

 forms have an elongated base slightly turned np at the 

 prow, a posterior outline deeply indented above the basal 

 process, an anterior outline Avith a slight projection below 

 the great fang, and a somewhat convex inferior (basal) out- 

 line. The main fang is proportionally large in comparison 

 with the neck and the tooth above it is of moderate size. 

 A feature of these hooks is that whilst in lateral view the 

 prow is narrowed toward the point, in a view from above the 

 end of the prow is flattened and chisel-shaped. The unci- 

 nigerous processes, which are somewhat prominent poste- 

 riorly, continue to the end. The row of hooks is on the 

 anterior face of the tip. lu the large northern variety from 

 Shetland and the Hebrides the base of the hook is somewhat 

 thicker posteriorly. 



Dorsally tlie cephalic plate in the twentieth sj)ecies^ 

 Poly cirrus elisabetlue, M'^Intosh, arises in front of a pro- 

 minent ring somewhat crcscentic anteriorly and apparently 

 continuous with the post-oral segment. The supra-oral 

 frill is similar to that of P. aurantiacus, but its lateral folds 

 differ, the boss or projection caused by them being farther 

 forward and more conspicuous, and in the prejjaration the 

 median fissure runs to the anterior border and forms a spout- 

 like projection there. The tentacles have a similar structure, 

 and form a mass like that of the common species. When 

 extended the cephalic plate forms a wide and frilled margin 

 to the funnel-shaped oral region, and the median scute is 

 smoothly rounded ventrally. 



The body has a similar outline to that of P. aurantiacus, 

 but the species is smaller, and the posterior margin finely 

 tapered, the edges being serrated by the uncinigerous pro- 

 cesses, whilst the anus has two dorsal papillae and a more 

 prominent mid-ventral papilla. The surface is rounded 

 dorsally and grooved ventrally. Anteriorly the mid-ventral 

 shield is proportionally larger than in P. aurontiacus, and 

 is somewhat lozenge-shaped in form, the anterior angle 

 being carried forward to the mouth. Behind it is a narrow 

 fillet followed by seven pairs of conspicuous glandular scutes 

 and a series of smaller which follow. Glandular extensions 

 occur laterally at each setigerous process. The segments 

 are marked by narrow rings as in the former species. So 



3* 



