Gatty Marine Laboratory ^ St. Andrews. 173 



segment has lamellae and dorsal and ventral bristles like the 

 4th^ and winged hooks commence on the ventral division of 

 the 7th, where also the branchiae originate. The winged 

 hooks (PL V. fig. 6) do not offer any diagnostic feature 

 except their small size, a single spur occurring on the 

 crown above the great fang. In contrast with Polydora 

 fiava, the lamellae o£ the feet generally and the bristles are 

 shorter, whilst the hooks project similarly in botli. The 

 species seems, so far as known, to be sparingly distributed. 



The Polydora hamata of Langerhans* also possesses a 

 smoothly rounded prostomium, and the sides of tlie peri- 

 stomium form a blunt cone. The great hook-like bristles of 

 the 5th segment, however, somewhat resemble those of 

 Polydora ffava, nnd thus differ from the foreging. The 

 ventral hooks, moreover, have a brown belt on the neck, and 

 the last 30 segments, or thereabout, have hook-like bristles, 

 after the manner of Polydora hoplura, whilst the anal funnel 

 is 4-lobed — all points of divergence from the preceding 

 form. 



The fifth and last of the series is Polydora hoplura, 

 Claparede, which extends from the Outer Hebrides to 

 Plymouth, and is also found on the east coast at St. Andrews. 

 The head is similar to that of Polydura ciliatu, except in the 

 absence of black pigment in the preparations. The pro- 

 stomum anteriorly has a median notch and two rounded 

 lateral regions. The arrangement and shape of the lamellae 

 and bristles of the first four bristled segments are like those of 

 P. ciliata. The fifth segment has hook-like bristles which 

 are distinguished at first sight from those of P. ciliata by 

 the parallel arrangement of the tips in situ — a feature due 

 to their more uniform diameter, — by their peculiarly curved 

 and by no means sharp tips, and by the position and size of 

 the lateral spur at the neck. The branchiae and winged 

 hooks commence on the 7th segment, the hooks having a 

 somewhat long main fang coming off nearly at a right angle 

 with a single spur above. The feature most diagnostic of 

 this species, viz. the hook-like bristles of the last 15 seg- 

 ments, is absent in the majority of the imperfect examples, 

 but where the caudal region is present the region occupied 

 by the hooks seems to be distinguished by the diminution of 

 the prominent tufts of bristles characteristic of the region 

 in front. The strongly curved and sharp hook-like bristles 



Op. cit. p. 92, Taf. x.\xiv. fig, 4. 



