268 PART II. SYSTEMATIC ACCOUNT 



Material: 20 tubes, 14 containing parts of animals. 



Locality: the Atlantic Ocean to the southwest of the British Isles (48°28'N 

 10°04'W; 48°32'N 10°10'W; 48°31'N 10°11'W; 47°50'N 8°08'W). 



Depth: 950-1685 m. 



Substratum: mud with an admixture of sand, Foraminifera, gravel and 

 stones. 



25. Siboglinum inerme E. C. Southward and A. J. Southward (Figs. 133— 

 A133) 



Southward, E. С and Southward, A. J., 1958b: 627, 628, 630, 632, Figs. 1, 3 (as S. 

 inermis); Southward, E. C, 1959: 444 (orthography corrected); Ivanov, 1960a: 1541 (as 

 S. inermis); Ivanov, 1960c: 5, 27, 78, 105, 185, 195-8, Figs. 87, 133 (as S. inermis). 



This species, collected on cruises of R.V. Sarsia in the Atlantic Ocean to 

 the southwest of the British Isles, was described by Southward and South- 

 ward, who had then 20 tubes at their disposal, some containing animals. 



[At the time of the Russian edition of this book Professor Ivanov had not 

 seen this species and he gave a description based entirely on the account and 

 the drawings by Southward and Southward. The account given below has 

 been amplified on the basis of notes provided by Dr. E. C. Southward upon 

 her original specimens and upon a few more collected in 1960. In life the 

 animal is largely colourless and transparent, but the cephalic lobe is brownish 

 and the glandular patches behind the bridle are whitish. The blood is red 

 because of the presence of haemoglobin. 



The fore-part of the body is cyclindrical and the mesosoma is four or five 

 times as long as the protosoma and divided from it by an obvious transverse 

 groove, which is continuous on the ventral side and interrupted on the dorsal 

 side (Fig. 133Д B). The smallish cephalic lobe is a little flattened dorso-ven- 

 trally, and the tentacle, as seen in the living animal, lacks pinnules. A post- 

 tentacular annular groove is always present, but it is not always complete 

 dorsally. The narrow keels of the bridle are always well separated dorsally 

 and usually joined ventrally, but sometimes just separate (Fig. \33A y B), 

 and in front of them runs a mid-ventral furrow which is not always well 

 marked. Immediately behind the bridle are situated lateral glandular patches 

 of epidermis, representing a glandular girdle interrupted both dorsally and 

 ventrally. These patches are readily visible in the living animal but rarely 

 seen in preserved specimens. The groove dividing the mesosoma from the 

 metasoma is simple and the dorsal ciliated band begins just a little behind 

 it. The rather broad ventral sulcus (Fig. 133 A, B) is bounded by up to 

 47 pairs of metameric papillae, but more usually there are between 30 and 40. 



