PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 187 



140 fathoms, apparently of the same species, liad a narrow ring- of blue 

 around the body, behind the head. Length, 50"'™ to 100™'"; diameter, 

 2.5™™ to 3""™. 



Common in the Gulf of Maine and Massachusetts Bay, on muddy bot- 

 toms, in from 30 to 140 fathoms. 



NEMATODA ? 

 Nectonema, gen. uov. 



Body long, slender, nearly round, smooth. Head without appendages, 



obtusely rounded or blunt-conical, apparently with the mouth on the 



under side. Along each side of a considerable part of the length of the 



body, posteriorly, there is a delicate fin, composed of very numerous, 



slender, hair-like processes, apparently in two close alternating rows 



(perhaps in life connected together by a delicate web). In the supposed 



male, the tail is more or less incurved, tapered to a small i)ai)illiform tip. 



Ko external sexual organ visible. In the larger form, regarded as 



female, the posterior end is subtruncate, with a small terminal papilla. 



Nectonema agilis, sp. uov. 



A long, slender, and exceedingly active, round worm, resembling a 

 Gordins, found swimming at the surface with a rapid, eel-like, undula- 

 tory motion. Integument firm, opaque, generally smooth, but with 

 minute, oblong, brown verrucie posteriorly. Body, in hfe, nearly round, 

 slightly flattened on two sides, of nearly uniform size throughout, but 

 slightly tapered close to the somewhat smaller, depressed, obtusely coni- 

 cal head, and somewhat more gradually tapered to the ijosterior end in 

 the male. The peculiar fins are generally more or less injured, even in 

 life, so that their real length is difficult to determine; but they appear 

 to occuijy half the length of the body, and perhaps more. In lite they 

 ai^pear to have a continuous web, binding the hair-like rays together, but 

 whether it was anything more than mucus is uucertahi. The fin-rays, in 

 length, are more than half the diameter of the body. Owing to the opacity 

 of the integument, little could be seen of the internal structure without 

 dissection or the i3reparation of transverse sections, for which no suit- 

 able opportunity occurred. In the head, which is more translucent, there 

 appeared to be four roundish bodies, visible by transmitted light, while 

 a transverse whitish band behind tbese seemed to indicate the position 

 of the mouth. At the posterior end there seemed to be an anal oi>euing, 

 and a straight intestine leading to it. In some female specimens, a cen- 

 tral whitish line, due to an internal organ (intestine f), could be traced 

 from the head to the extreme posterior end, and a yellowish white organ 

 (ovaries ?), with numerous transverse divisions, extending from near the 

 head to the tail, could be indistinctly seen. Color, in life, grayish or 

 yellowish white, with four narrow, double, longitudinal lines of dark 

 slate-color. Length, 80™™ to 200™"'; diameter, O-S"""^ to 1™™. 



Vineyard Sound, Mass., swimming actively at the surfiice in the 



