.Annelida. 



8, Umbellisyllis fasciata, M, Sars, 



nov. gen. et sp. 

 (Plate 4. fig. 12 18). 



I have seen some specimens of this beautiful Annelide from different parts of our 

 coast, and from very different depths. Usually however it appears to have its proper dwel- 

 ling place in the greater depths about 100 fathoms and downwards; and this is probably the 

 reason why it has formerly quite escaped the attention of Naturalists notwithstanding its very 

 remarkable and unusual coloring, which preserves itself tolerably well, even in specimens that 

 have been kept a long time in spirit. 



In preparing the following description, and particularly the concluding remarks, I have 

 been greatly aided by my Father's manuscript notes. 



The body attains a length of about 24 Mm., and a breadth over the middle (from foot- 

 point to foot-point) of 3 Mm.; towards the anterior end it is somewhat tapered (see fig. 12) 

 and towards the posterior end considerably so. Thus the body is not very long in proportion 

 to its width. The back is convex (see fig. 16) with rather abruptly declining sides; but 

 the ventral side is flat or rather concave along the middle, shewing a wide and shallow longi- 

 tudinal ventral furrow. The number of the bristle-bearing segments varies according to the 

 size: in the largest specimens it is as great as 65 while in smaller it is not more than 46. 

 The segments are (see fig. 15) very short -- 5 6 times broader than long; the last (the 

 anal segment) is (see fig. 17) very small, button-like and furnished with 2 conically pointed 

 anal filaments, which are about as long as the 2 nearest segments taken together. 



The head (see fig. 13) which is somewhat sunk in the 1 s . 1 bristle-bearing segment, and 

 slightly smaller than the same, is nearly square, with convex side-borders, broader than it is 

 long, its upper surface convex; the anterior border strongly hollowed forming 2 very short 

 triangular frontal lobes, standing out far from each other, and somewhat curved downwards, 

 separated by a transverse furrow from the rest of the head; the posterior edge, which is 

 straight, is hidden by a membrane (a), which will be mentioned subsequently, and which fre- 

 quently covers also the posterior part of the head. 



The head bears 3 tenlac'lc* of about equal size, which are cylindrical, tolerably thick, 

 very short (Y 4 Vs f the width of the head) and not articulated, with obtusely rounded ex- 

 tremity. The 2 paired tentacles are situated on, or properly speaking quite close behind, the 



