Gatty Marine Lahoratory^ St. Andreios. 169 



angle from tlie throat, and with a small spike on the crown. 

 At the 30th foot at least a dozen of these organs project 

 from the surface. 



Just in front of the tail the dorsal cirrus is moderately long 

 and subulate, and occasionally it shows a basal enlargement. 

 The dorsal bristles project for a third of their length beyond 

 the tip of the cirrus. The region between the divisions of 

 the foot is convex, and below the row of 7 or 8 hooks 1 or 2 

 curved bristles project. Tlie convexity of the curve is 

 outward. 



Formerly, in consonance with the Catalogue of the British 

 Museum, it was supposed that only one species of Polydura 

 occurred in British waters, but more extended examination 

 shows that at least five species are found in our seas besides 

 Polydora c<eca, ffirsted, entered in the fauna of Plymouth, 

 but which has not yet beea examined at St. Andrews. The 

 genus (founded by Bosc) was fivst clearly described by 

 Claparede, who, however, included it under the Ariciidje. 

 The first species, Polydora cUiata, Johnston, has the pro- 

 stomium elevated and terminating anteriorly in two rounded 

 lobes with a median notch, the ridge passing backward to 

 tlie 3rd segment. !^'our black eyes are on the ridge, and 

 dark pigment occurs at its sides and in the furrows of the 

 first four segments. The body is largest in the anterior 

 third, flattened dorsally and rounded ventrally, tapered a 

 little anteriorly and more distinctly posteriorly, where it ends 

 in a cup-like process with a dorsal notch. The segments 

 lire from 60-75 in number. The branchite commence on 

 the 7th foot and their number ranges from 22 to 31. 

 Thus they differ from Mesnil's form of P. cUiata. The first 

 foot has a dorsal lamella but no bristles, but the latter 

 occur throughout the rest of the body. The fifth bristled 

 segment has large hook-like bristles, the tips are curved, 

 more or less acute, and have a small spur on the neck. 

 This form is very widely distributed in European waters. 



The second is Polydora fluva, Claparede, which extends 

 from Shetland to the Channel Islands and is common in the 

 Mediterranean. The bifid prostomium is usually longer than 

 in Polydora ciliata and the divergent processes more distinct. 

 A little pigment occurs on each side of the prostomium in 

 front. Eyes are not visible in the preparations. The median 

 ridge of the snout reaches the fourth bristled segment. The 

 body is of considerable proportional size (2 inches or more 

 in length) in contiast with P. ciliata, but of similar cou- 

 Ann. & May. X. Hint. ;Ser. 8. Vol. iii. 12 



