228 



PART II. SYSTEMATIC ACCOUNT 



of 6-5 : 1, is noticeably flattened in the dorso-ventral direction. The boundary 

 between the protosoma and the mesosoma is unclear, but there is an annular 

 groove immediately behind the base of the tentacle (Fig. l\6A, В, C). The 

 tentacle is attached so near the front end of the body that the cephalic lobe 

 takes up a quite inconsiderable fraction, about one-ninth, of the total length 



Fig. 116. Siboglinum microcephalum: A - front end of the body in ventral view, В - from the dorsal 

 side, and, С - from the left side; D - the region of the girdles in ventral view, and, E - in dorsal 

 view; F - part of a girdle (on one of the toothed platelets the bases of the teeth are indicated); 

 G - part of the postannular region of the metasoma with a dorsal shield ; H - ventral papilla of 

 the postannular region. 



an - girdles; с - cephalic lobe; ci - glandular girdle; со - dorsal ciliated band; da - anterior group 

 of teeth; dp - posterior group of teeth;/- keel of the bridle; m - bundle of muscle fibres seen by 

 transparency; tns - mesosoma; p - cuticular plaque; pa - papillae; ps - protosoma; s* - groove 

 between the mesosoma and the metasoma; s* - post-tentacular groove; sc - dorsal glandular shield; 

 sv - ventral sulcus; t - tentacle; v - ventral papilla of the post-annular region of the metasoma. 



