42 



transversal furrow which bounds the frontal lobes, at a considerable distance from each other; 

 the third or single tentacle stands far behind them in the middle of the crown, not far from 

 the posterior border of the head, so that its basis is not unfrequently covered by the above 

 mentioned membrane. There are 2 pairs of eyes of round shape and bright brown red color, 

 which are situated somewhat nearer to the side-borders of the head than to its medial line: 

 the anterior eyes some distance behind the paired tentacles, the posterior eyes in a line with 

 the single tentacle ; the latter are a little nearer to each other than the former, and are also 

 nearly twice as large as the anterior, close in front of which may further be observed a pair 

 of extremely small black points, that may perhaps be considered as a third pair of eyes as 

 in several other Syllides. 



At the posterior extremity of the head, or just in the transversal furrow which sepa- 

 rates it from the first segment, is situated a large soft thin leaf-like semilunar membrane (fig. 

 13. 14. a) which is placed horizontally or across the axis of the body, and with the central 

 part of its concave border attached to the body, but otherwise freely projecting and more or 

 less erect; its convex or free border lying usually beyond, and covering the posterior part of 

 the head; both its rounded side-corners, or ends of the crescent, being likewise free. It is 

 about twice as wide as high, about as wide as the head; its free border (and, as it appeared 

 to me, also its surface) is thickly covered with short and fine, in a living state vibratory, cilia. 



The bucal segment, .which projects only a little beyond the head, shews on its anterior 

 extremity (see fig. 14) the rather large round mouth, on the thick border of which there are 

 observed 5 small raised round nodules or papillae; one ventral and 2 lateral on each side; 

 close behind the upper pair of these papillae, there is situated on each side of the segment 

 a tentacle, which in form and size completely resembles the tentacles of the head. 



The feet (the pedal nodes) which enclose one single thin needle pointed at the end, 

 and a fascicle of very long and thin bristles, are situated far down on the body, so as nearly 

 to go Hush with the flat ventral side (see fig. 14. & 16). They are nearly cylindrical, yet 

 somewhat compressed from the front backwards, proportionally rather long (about V 4 of the 

 width of the body), and have at the extremity, on the side of the rounded bristle-bearing node, 

 a conical process projecting beyond the same; and below, close to 'the extremity of the foot, 

 a similar one but somewhat longer, which properly seems to represent the ventral filament. 

 The dorsal filament is not attached to the foot, but some distance above it on the side of 

 the body. It is cylindrical, filiform, not articulated, longer than the feet, and even reaching 

 to the end of their bristles, and its extremity is obtusely rounded. At the posterior end of 

 the body (see fig. 17) the pedal nodes, as well as the dorsal filaments, diminish very rapidly 

 and suddenly in length, so that in the extreme segments they are quite rudimentary. The 

 pedal bristles (fig. 18) in each foot about 20 in number, project very far, and are composed, 

 or consist of a very long straight shaft, on the obliquely truncated extremity of which is fixed 

 a rather short linear, or knife-like terminal appendage. They belong therefore to the so- 

 called thorny bristles (setae spinosae). 



