SIBOGLINUM SILONE 293 



papillae lie at even intervals along its ventral side (Fig. FF1337 7 ). Numerous 

 epidermal gland cells are found near each papilla, especially on the dorsal 

 surface of the trunk where they form a primitive dorsal glandular shield 

 (Fig. FF133/ 1 ). These cells are very like the epidermal gland cells of the 

 preannular region. 



No sexual products have been observed in this animal. 



The tentacle is 11 mm long, the fore-part of the body 1-65 mm long and 

 the mesosoma 0-2 mm broad. The metameric part is 6-5 mm long and the 

 whole preannular region 20 mm long. The preserved part of the postannular 

 region is 6 mm long. The whole animal, including the tentacle, is about 39 mm 

 long though, since a considerable part of the postannular region seems to be 

 missing, the real length must be greater. 



The torn-off tube from which the animal was extracted is 95 mm long and 

 0-13 mm in diameter. The tube is very soft and elastic, comparatively colour- 

 less transparent and structureless, lacking both rings and segmentation. Its 

 front part is wrinkled with soft transverse ridges (Fig. FF133G). 



S. arabicum is like S. subligatum in lacking pinnules, but it is distinguished 

 from it by the lack of a waist between the mesosoma and metasoma, by the 

 rather greater development of the glandular patches of epidermis and by the 

 unringed tube. 



Material : One tube containing an animal. 



Locality: Vityaz' station 4726 (31st cruise): Indian Ocean, Arabian Sea 

 at the entrance to the Gulf of Aden, to the northwest of Socotra Island. 



Substratum: brown-grey mud. 



Depth: 2385 m.] 



[33. Siboglinum silone sp. nov. Ivanov (Figs. GG133-LL133) 



This interesting species was first found in the Arabian Sea to the west of 

 the South Indian coast, together with Diplobrachia southwardae sp. nov. and 

 Lamellisabella minuta sp. nov. Later it was also found in the Gulf of Aden. 

 I have had four complete specimens at my disposal, together with seven 



Fig. FF133. Siboglinum arabicum: A - fore-part of the body in ventral view; В - nonmetameric 

 part of the trunk ; С - region of the girdles from the right side ; D - part of a girdle ; £ - toothed 

 platelet ; F - a postannular ventral papilla from the right side ; G - tube. 



ag - ventral glandular region of the mesosoma ; an - girdles ; с - cephalic lobe ; da - anterior group 

 of teeth ; dp - posterior group of teeth ; f- bridle ; g - glandular portion of integument ; ms - meso- 

 soma ; mts - metasoma ; pa - metameric papillae ; pa 2 - papilla in front of the girdles ; ps - proto- 

 soma ; s 2 - groove between the mesosoma and metasoma ; sv - ventral sulcus ; t - tentacle ; tl - lateral 

 glandular tract of metasoma; tg - glandular ribbon of the mesosoma; v - ventral papilla. 



