, 70 DISCOVERY REPORTS 



results have been considered when discussing the distribution of individual species. The charts 

 showing distribution do not, however, show the negative stations (except Text-figs. 23 and 24 and 

 Tables 14-19) although it is highly desirable to indicate the regions from which a species is absent. 

 The reason for this omission is the difficulty of defining a negative station. Many species are taken 

 mostly, but not exclusively, in certain nets and all nets were not always used at all stations. Moreover 

 the same number of samples was not collected at every station. Thus, although a species may not 

 have been collected at a particular station, this station may not necessarily be a negative one. The 

 species-distribution charts should therefore be compared with the charts for all the stations examined 

 (Text-figs. 1-5); in this way a fair idea is obtained of presence and absence in the area covered. 



SYSTEMATIC ACCOUNT 



A considerable literature exists on the systematics of pelagic polychaetes, of which the most com- 

 prehensive is the report by Stop-Bowitz (1948) on the 'Michael Sars' North Atlantic Deep-Sea 

 Expedition in which many nomenclatorial problems are clarified. These include the replacing of 

 numerous long-established names by others which have priority but which for various reasons have 

 been overlooked. I have accepted most of the conclusions reached by Stop-Bowitz and reference can 

 be made to his paper for greater detail. Lists of synonyms preceding the descriptions of species have 

 been restricted to works important to distribution in the Atlantic Ocean, and to references of syste- 

 matic value ; the spelling of specific names in these lists follows that used in each particular reference. 



The remoteness of the regions in which many pelagic polychaetes occur has resulted in our having 

 little or no knowledge of the living animal. Minute morphological differences therefore have 

 frequently been accepted as specific characters, when they may in fact indicate geographical 

 variants or different stages in life cycles. It is emphasized below that this is particularly true of the 

 Alciopidae. 



All specimens recorded for the first time in this report have been deposited in the British Museum 

 (Natural History) Collections (Registered numbers, 1955:6:1:1 to 2849, 1955:6:2:1 to 2291 and 

 1955:6:3:1 to 2507). 



Family TOMOPTERIDAE 



All species in this family are exclusively pelagic in habitat and aberrant in form, never having more 

 than two pairs of chaetigate processes and having over most of the body achaetous parapodia with 

 paddle-shaped pinnules. 



Prostomium with a pair of laterally directed antennae, which together form its anterior border, 

 a pair of nuchal organs and normally a pair of eyes. There may be two pairs of lateral chaetigate 

 processes just behind the eyes — of which the anterior and smaller pair is often missing (the first pair 

 of chaetigers), whereas the posterior pair is always present (the second pair of chaetigers). Parapodia 

 are biramous and achaetous with notopodia and neuropodia modified into paddle-shaped pinnules; 

 these pinnules may carry glands of unknown function which have been given the following names : 

 (a) chromophil glands; these are large glands which appear only in neuropodia and stain deeply with 

 haematoxylin ; (b) hyaline glands; very small glands which occur in either notopodia or neuropodia, 

 they may be pigmented or appear only as crystalline spots; they do not stain with haematoxylin; 

 (c) rosette glands; very small glands which occur on the trunks of the parapodia or on notopodia and 

 neuropodia; they do not stain with haematoxylin; (d) spur glands; these are small, normally sub- 

 sidiary to the chromophil glands, and occur only on neuropodia; they stain with haematoxylin. The 

 spur gland is so called because it projects from the normally entire surface of the pinnule. Posteriorly 

 the body may be prolonged into a tail bearing rudimentary parapodia. Throughout his work on 



