ZENKEVITCHIANA LONGISSIMA 391 



latter, oval in shape and reaching 40-60/u, across, are thin and delicate, but 

 have a thickened front edge (Fig. 154C). The girdles, lying on muscular 

 ridges, are interrupted ventrally and the first girdle dorsally also (Fig. 

 15-Ш, £), while the hind girdle arches sharply forwards on the dorsal side. 

 The yellowish oval toothed platelets, 13— 17/x long, form three to four rows in 

 each girdle (Fig. 154jP, G). About a third of each platelet is covered by the 

 numerous very small teeth of the anterior group, while those of the posterior 

 group are comparatively large, but fewer (Fig. 154//). Behind the girdles lies 

 a mid-ventral papilla (Fig. 154/)) with a very small plaque. The postannular 

 region of the trunk is also very long and cylindrical and the small adhesive 

 papillae are here arranged on. the ventral side in transverse metameric rows, 

 with eight in each row (Fig. 154/). Variants not infrequently occur, however, 

 with a smaller number of papillae in each row, with the papillae not in a 

 straight line, or with single isolated papillae between the rows. Each papilla 

 has a slightly bent, rod-shaped plaque not more than 80/x long (Fig. 1547). 



In two individuals of medium size the length of the body, including the 

 tentacles, amounted to 36 cm in the male and 35-5 cm in the female. The 

 tentacles are usually 5-6 cm long and in one specimen reached 9T cm. 

 The fore-part of the body is up to 5 mm long, with a breadth, at the level 

 of the bridle, of up to 0-8 mm. 



The spermatophores are much elongated, gradually tapering towards the 

 afilamentar end and with the greatest breadth quite near the filamentar end 

 (Fig. \55A). They resemble the spermatophores of Spirobrachia grandis and 

 S. beklemischevi, except that they are much narrower. The basal part of the 

 very long filament is stout and has a granular structure, but gradually tapers. 

 The whole spermatophore is с . 1-5 mm long. 



The tube of Zenkevitchiana longissima is rather peculiar. It is white, rather 

 flexible and elastic, and the walls are very stout, consisting of a dense semi- 

 transparent substance, which is easily cut with a sharp scalpel. Almost the 



Fig. 154. Zenkevitchiana longissima: Metasoma: A - hind part of the metameric section of the pre- 

 annular region in ventral view; В - part of the non-metameric section of the preannular region in 

 ventral view; С - cuticular plaque; D - region of the girdles in ventral view; E - the same in dorsal 

 view; F - one half of a girdle under high magnification; G - part of a girdle; H - toothed platelet 

 (in the front part of the platelet the bases only of the teeth are indicated) ; / - part of the post- 

 annular region in ventral view; J - ventral papillae of the postannular region. 

 an - girdles ; da - anterior group of teeth ; dp - posterior group of teeth ; gt - pyriform glands seen 

 by transparency; p - cuticular plaque; pa - papillae; pa 1 - papillae lying behind the girdles; 

 pa? - transverse row of papillae ; vv - ventral blood vessel seen by transparency. 



