152 " ENDEAVOUR " SCIENTIFIC RESULTS. 



furrow, nearly longitudinal, which, however, curves outwards 

 anteriorly and ceases before it reaches this end (PI. xlviii., 

 fig. 40). The anterior end is rounded, and its thin margin is 

 somewhat "upcurved. Along each side of the prostomium is 

 an upstanding lamella, whose thin upper edge is entire, and 

 posteriorly is continuous with the margin of the peristomium. 

 The prostomium is dorsally overhung by a transverse flap of 

 the peristomium, which is also entire. If this flap be lifted 

 up the prostomial platform or flattened ridge is seen to extend 

 below it for about half the length of the peristomium ; this 

 concealed portion is equal in length to the exposed portion of 

 the platform. 



The peristomium is biannulate, the posterior annulus 

 being about half the length of the anterior, which is traversed 

 by a horizontal furrow on each side dividing it into an upper 

 and a lower portion, which latter is prolonged into the 

 marginal lamella of the prostomium (PI. xlviii., fig. 38). 



The ventral surface of the head is flat, and the mouth is a 

 longitudinal slit widened posteriorly into a nearly circular 

 aperture, which lies at about the middle of the anterior 

 annulus of the peristomium (PI. xlviii., fig. 39). 



The second segment and the four following are biannulate ; 

 the anterior annulus is chfetigerous and about twice the 

 length of the posterior. The segments gradually increase in 

 length, so that the distance between the 6th and 7th bundles 

 of chaetae is about twice that separating the 2nd and 3rd 

 bundles, the actual distances being 9 mm. and 5 mm. 

 respectively. 



Each of the segments 4, 5, 6 and 7 has a lateral glandular 

 cushion along its entire length, which reaches up the side 

 as far as the notopodium, but on the 8th this glandular 

 cushion is limited to a quadrate area round the torus 

 uncinigerus. 



The first chsetigerous segment, which succeeds the peri- 

 stomium, has only dorsal capillary chsetse, arranged in a 

 vertical fan-shaped bundle protruding from a two-hpped 

 notopod. 



In the following segments there is, in addition, a ventral 

 torus uncinigerus, in which the hooks are arranged in a 

 single row. This torus is very short in the third segment, 

 rather longer in the fourth, and attains its full development 

 in the fifth, where it is nearly half the height of the body. 



