'^°i89ll'"] PROCEEDINGS OF THE NATIONAL MUSEUM. 295 



liook. About twelve unciui ou lirst setigerous somite, iiicreasiuf,' to 

 thirty posteriorly; color greeuish, often with red or yellow shades. 

 Fourth to seventh somites often dark. Length up to 80 millimetres; 

 diameter, 2 millimetres. 



As defined by Malmgren, this genus should have four preanal somites 

 without setie, but Langerhans has already placed one form here with 

 but two such somites, tliinking that the numl)er is not of as much con- 

 stancy as Malmgren supposed. In all other respects this Beaufort 

 species fits very well into Malmgren's genus. 



This is one of the most .abundant Annelids found at Beaufort ; its 

 sand tubes stand quite close together over large areas of Bird Shoal, 

 projecting above the sand and often bearing a clear, gelatinous mass, 

 cylindrical with rounded ends and about an inch long in which numer- 

 ous eggs are inclosed. In these masses, exposed alternately to the air 

 at low tide and to the water at high tide, the eggs develop and the 

 young remain often till quite advanced. It is, I believe, this species 

 the eggs of which have been in part the subject of Professor Wilson's 

 paper on the segmentation of Annelids, though it was there referred to 

 as ChjmeneUa torquata (Johns Hopkins University Studies, vol. 2). 



As these masses completely close the orifice of the tube the Annelid 

 makes a new opening a few inches below the surface of the sand and 

 thence builds up a second branch, forming thus a Y shaped tube, one 

 arm of which is closed at the end by the egg mass, while the other 

 gives the Annelid access to the water. 



t) 



PETALOPROCTUS Qiiatrefages. 



(The species described below is referred to this genus as being proba- 

 bly closely related to the forms described by Quatrefages; yet it would 

 be perhaps better to form a new genus for it.) 



Petaloproctus socialis, sp. iiov. 

 (Plate xvn, Figs. 3G-41.) 



Body elongated, composed of twenty-three somites, of which twenty- 

 one are setigerous. Buccal somite twice the length of first setigerous 

 somite; anal somite equal to buccal ; second to fourth setigerous somites 

 gradually increasing in length; fifth to seventeenth somites much 

 longer; seventeenth to twenty-first decreasing rapidly; twenty-lirst 

 an inch shorter than anal. Form of head varying much according to state 

 of contraction ; when expanded conical, Hat below, rounded above, 

 somewhat truncated above, ending in a crescentric rim or ridge bear- 

 ing red pigment spots on the side, from which rim a median elevation 

 runs back dorsally half the length of the head, separating a depression 

 ou the right from one on the left, while these in turn are divided by a 

 slight elevation into an anterior and a posterior part. Mouth ventral 

 near the anterior end of the head. Anal somite truncated dorsally and 



