38 O. O. Sars. 



a veiy slight depression, from which a distinct suture runs 

 downwards to the insertion of the mandibles. 



The head (see figs 3 & 5) is exceedingly large, and is 

 prolonged below to a broad and curved rostral expansion, on 

 the inside of which the richly ramified cœcal appendages of 

 the intestine (liver) may be traced. This expansion exhibits a 

 well-marked and rather high dorsal keel, which in its outer 

 part is abruptly bent, and terminates in an obtuse point 

 forming the extremity of the rostrum. Along each side of 

 the head extends a very conspicuous, prominent crest (the 

 fornix), dividing it into a dorsal and a ventral area. This crest 

 runs from the upper insertion of the mandibles obliquely for- 

 wards, and about in the middle, curves abruptly down the 

 sides of the rostrum as far as its extremity, where it meets 

 the dorsal keel. At the point of its greatest curvature, the 

 fornix is joined on each side by another less distinctly defined 

 and rather short transverse keel originating from the front in 

 the region of the eyes. When viewed in front (fig. 4), the 

 head appears moderately broad in its proximal part, becoming, 

 however, considerably instricted at the origin of the rostral 

 part. The latter exhibits in this view a rather regular lingui- 

 form shape, being obtusely rounded at the tip, and having no 

 lateral projections. 



The hind division of the body (see fig. 3) is rather thick 

 in front but rapidly tapers distally, and is less distinctly 

 curved in its posterior part than in the 2 preceding genera. 

 It is divided into a rather restricted number of segments, 

 being only 12 in all, besides the very small tail-piece. All 

 the segments are quite smooth above; but from each side of 

 the 2 last ones originates a peculiar leaf-like expansion (see 

 figs 3, 10, 11), which extends laterally, and sometimes may be 

 found slightly deflexed, sometimes more reflexed. The edges 

 of this expansion are divided into 3 acute, and somewhat 

 curved lappets, and on the dorsal side, moreover, 2 smaller 



