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PART II. SYSTEMATIC ACCOUNT 



contraction of the animal (Fig. 97 'A 9 B). A barely discernible transverse groove 

 runs a little in front of the bridle, parallel to the keels, arching forward on the 

 dorsal side and making a sharp backward bend in the mid-ventral line 

 (Fig. 91 A, B), while the protosoma bears a pretentacular groove, which 

 curves backward on the dorsal side (Fig. 97 B). The long stout tentacle is 

 furnished with a double row of comparatively large, bow-shaped bent 

 pinnules (Fig. 98Л, B), but on the proximal part they are absent. The 

 cephalic lobe is small and conical. 



The bridle is placed near the front end of the mesosoma and its brownish 

 keels are rather prominent and uniform in thickness. They are joined 

 together ventrally, but not on the dorsal side, where, however, they very 



Fig. 97. Siboglinum ekmani: A - front end of the body of a female in ventral view; В - the same 

 from the dorsal side ; С - part of a girdle of toothed platelets ; D - a toothed platelet from the side ; 

 E - part of the post annular region in dorsal view; F - the same from the left side. 

 с - cephalic lobe; eg - gland cell; со - dorsal ciliated band; da - anterior group of teeth; 

 dp - posterior group of teeth; /-keel of the bridle; ms - mesosoma; />-cuticular plaque; 

 pa - papillae ; pgt - pore of pyriform gland ; ps - protosoma ; s 1 - groove between the protosoma and 

 the mesosoma; s 2 - groove between the mesosoma and the metasoma; s 3 - pretentacular groove; 

 se - dorsal glandular shield; sv - ventral sulcus; t - tentacle; v - ventral papilla; vd- dorsal blood 

 vessel. 



