614 A. E. Verrill — Turbellaria, Nemertina^ and 



nse are shorter, only projecting a little beyond the palpi. The upper 

 tentacular cirri are similar to the tentacle and of about the same 

 length. The lower ones are about ^ shorter. 



The 1st dorsal cirrus is similar to the upper tentacular cirrus, but 

 longer. The 2d is very much shorter, and the succeeding ones rap- 

 idly decrease in length, those beyond the gastric region being only 

 1/5 to 1/6 as long as the diameter of the body, or even less, and con- 

 sisting of only a few annuli (often only 3 or 4) and scarcely longer 

 than the parapodia. 



Setae very few ; anteriorly there are usually 1 or 2 rather strong 

 simple bidentate setae and one acute aciculuin, which rarely pfojects ; 

 posteriorly there is generally only one bidentate seta3, which is 

 longer and larger than the anterior, and a single aciculum, which 

 often has a bent, hook-like tip. No blades were found on any of the 

 setae of numerous specimens examined. The bidentate setae, which 

 correspond to the stems of compound setae, have a simple, incurved 

 or slightly hooked tip, with a strong triangular tooth below it, the 

 intervening space being concave and oblique. Possibly a blade 

 may be present in the very young. The anterior parapodia are 

 short; the posterior ones become more elongated. 



The oesophagus is rather short and wide, pigmented with opaque 

 green, so that its form is not easily seen; median tooth near the edge, 

 acute conical, its end projecting beyond the aperture ; margin 

 incurved and usually indistinct, but minutely denticulate, at least in 

 some cases. Soft pharynx with about 10 rounded lobes. Stomach 

 barrel-shaped, usually a little shorter and not much thicker than the 

 oesophagus, opaque, the rows of glands poorly defined ; sometimes 

 the stomach and oesophagus are about equal in length, or the 

 stomach may be the longer, owing to the frequently crumpled and 

 contracted condition of the oesophagus. 



Color, in formalin, is yellowish white; the tissues are more opaque 

 than in most species. Length, 4 to 6°"™ ; diameter, .5 to .6™'". 



Taken in large numbers on one occasion. It inhabits sponges. 



Easily distinguished from the young of other species by the large 

 palpi, head, and anterior segments, and the extreme shortness of all 

 the cirri, except those of the head and first segment. The small 

 number of the setje and their peculiar tips are also characteristic. 



This is allied to H. hamata of Europe and Madeira, which has the 

 tips of the simple setre trifid, and to //. tentaculata {Max. 1879, as 

 S. spongicola, var.), which has much longer cirri and trifid setae. 



H. streptocephala (ffirst and Grube), from St. Croix, has longer cirri. 



