218 Proceedings of the Royal Irish Academy. 



towards the anterior end, with broad hands of deep-red surrounding the hody 

 at intervals (pi. 47, fig. 42)." 



External Struchtre. — The forward point of the head is rather short and at 

 the base hut little removed from the cephalic plate (fig. 5). The borders are 

 low, on the whole (fig. 7), though most distinctly so on the sides of the head ; 

 towards the hinder regions they diminish somewhat in strength and meet 

 here in a fairly definite angle, when the cephalic plate is more or less extended. 

 A lateral notch on each border can be seen at any rate on individuals with 

 strongly compressed cephahc plates. 



Numerous ocelli (fig. 4; cf. 1, fig. 42a) are to be found in front of the 

 ■ mouth in a rather broad band, which extends some distance up, on the render- 

 side of the anterior point of the head, and which divides into two hands, as it 

 were, at one place in either side, fusing again near the median line. The 

 ocelli are distinctly reddish-brown, although the colour is fainter in youngish 

 individuals ; and similarly the number of ocelli in these individuals is not so 

 large as in older ones, especially towards the middle. The proboscis could 

 not be closely investigated in the material at my disposal. This much, how- 

 ever, can be said about it, viz. that it is perfect all round and has no extended 

 papillae. Moreover, no papillae whatever could be observed on the faint 

 ridges that run along the outer side of the proboscis — ridges which to the 

 number of 24 are to be seen in fig. 1. The nuchal organs are not especially 

 long and are separated by a rather broad but low keel (figs. 5 and 7). 



The front edge of the first setigerous segment is slightly bent forwards in 

 fiont of the parapodia. The length of the anterior setigerous segments 

 diminishes pretty evenly as far as the fifth setigerous segment, after which the 

 sixth and the seventh segments show a slight increase. On the last-named 

 the parapodia are situated somewhat in front of the posterior third. The 

 eighth setigerous segment is considerably longer than tlie one immediately 

 before it, and its parapodia, like those in the segments that follow, lie far to 

 the rear. These segments, to begin with, increase in length backwards ; and 

 the fifteenth and the sixteenth setigerous segments, in particular, are very 

 long, the sixteenth being the longest. The hindmost setigerous segments 

 diminish rapidly in length ; there are 19 setigerous segments in all. After 

 them there follow— very rapidly decreasing in length— 3 achaetous segments 

 (figs. 8 and 9), of which the last in particular is very short, with slight 

 remains of parapodia. The foremost of these segments at least has a distinct 

 posterior limit (fig. 8). Thereafter follows a callus- shaped ring which in 

 certain positions is markedly defined towards the rear (figs. 8 and 9] ; in 

 individuals that are not contracted at the commencement of the section 

 that thereafter follows, which is rather short and cup-shaped, the ring in 



