288 DASYBRANCHUS CADUCUS. 



the median sulcus of the segment, viz. project on a flattened papilla or process behind it. 

 Each hook (Plate CVII, fig. 15 a) has a slightly curved shaft tapered a little inferiorly, 

 gradually enlarging to the commencement of the wing, then narrowing to the throat, from 

 which the main fang comes off at a little more than a right angle, and with two teeth on 

 the crown above. The wings are fairly broad, and are rounded distally beyond the fang. 



Behind the last bristle-bundle a change in the segments is inaugurated, for whilst they 

 remain two-ringed the dorsal papilla for the bristles disappears, and a lateral groove is 

 gradually formed dorsally a little below the line of the bristles, this groove being rendered 

 more distinct by a prominent papilla which marks the second ring of the segment later- 

 ally, and indicates the line of hooks below it. The mid-ventral line now presents a groove 

 which continues for fully an inch backward. Instead of the bristles dorsally a line of 

 hooks— indicated at first by a slight inflection of the median groove of the segment — takes 

 their place. Ventrally a long band of hooks is present on each side, and by-and-by meet 

 in the middle line, so that this region of the body is mainly concerned with movements in 

 the tunnel in the mud or sand. 



About the sixtieth armed segment the rows of hooks have arranged themselves on a 

 long pad on each side dorsally, separated in the middle line by a considerable interval ; 

 whilst on the ventral surface the rows appear to meet in the middle line, so that a con- 

 tinuous series stretches from side to side, a slight inflection of the line in front and behind 

 in the centre indicating the seat of separation in front. 



Behind the foregoing region (sixtieth foot) the body in the preparation undergoes 

 considerable dilatation dorsally, and the ventral line of hooks ends on each side laterally 

 in a pale elevated ridge, which terminates abruptly superiorly, a pale striated region 

 occurring between it and the commencement of the dorsal rows, which are still separated 

 by a considerable interval. They are recognised by the opaque elevation in front and 

 behind. 



In the middle region the branchiae have the aspect shown in Plate 01, fig. 4 a. 



Moreover, in every segment in the posterior region an aperture exists about 

 the upper end of the ventral row of hooks, and out of this a small branchia projects. 

 Some are included until pressure is made on the body, and then they are distinct. These 

 apertures are at a higher level, for instance, than those of the ' Challenger ' form, Station 

 233 B, which are at each edge of the flattened ventral surface and have an elongated 

 glandular fillet above them. The position of the branchia? thus corresponds with the 

 description and figure of Olaparede from specimens procured at Port Vendres. 



In the intestine of the middle region are many ovoid masses of mud as in Chxtopterus. 

 These consisted for the most part of very fine amorphous mud of a pale brown colour, 

 with a few sand-particles, a few minute fragments of sponge-spicules, but very few 

 traces of softer tissue. 



The specimen appeared to be a female with small ova in the perivisceral cavity. 



Reproduction. — At Naples, where it is termed " Vierme ca lana," the period of 

 sexual maturity is from February to August. 



Claparede (1864) found this species at Port Vendres, and gives an interesting account 

 of its general structure, especially in regard to the branchiae and pedicled lateral sacs. 



The same author (1868) draws attention to the appearance of the mature male, in 



