46 LEIDY'S DESCRIPTIONS OF AMERICAN WORMS. 



Length I to 1| inches, greatest breadth at girdle ^ of a line, posteriorly | of a 

 line. 



Habitation and Remarks. — Found in the soft muddy bottom of shallow ditches in 

 the vicinity of Philadelphia. It is a very beautiful and graceful form. When not 

 elongated to the greatest extent, the median vessels with the white intestine (when 

 empty) form three spirals, which through the transparent skin have a very pleasing 

 effect. The anterior tip is whitish, the tail end yellowish. It moves with great ease 

 through the mud, and very frequently is found buried in the latter for the anterior 

 two-thirds of its length, with the tail end protruding vertically above the surface, 

 which it keeps in constant vibrating motion like the Saehuris variegata, Hoffm.* 

 When disturbed it disappears or withdraws the tail with astonishing rapidity. In 

 the spring of the year it deposits in the mud whitish, compressed oval sacs, from half 

 a line to a line in length, with a short tubular prolongation at each end, containing 

 from twelve to eighteen oval eggs about l-70th in. long. 



On April 2d, 1849, while walking in the outskirts of the city, I noticed in a shallow 

 ditch numerous reddish patches of from one to six inches square, which supposing 

 to be a species of alga, I stooped to procure some, when to my surprise I found 

 them to consist of millions of the tails of Strephuris agilis, all in rapid movement. 

 The least disturbance would ccause a patch of six inches square so suddenly 

 to disappear, that it resembled the movement of a single body. My friend 

 Dr. Bridges informs me, a few years since he met with a similar instance of such an 

 astonishing multitude of these worms. 



The curious movement of the tail I suppose to be secondary to respiration. Upon 

 it I have frequently noticed numerous bunches of a sessile species of vorticella. 



Aeolosobia, Ehrenhe7'g.-\ — Corpus filiforme, molle, distincte articulatum; singuli 

 articuli setarum fasciculis utrinque barbati ; ocelli nulli ; os anticum inferum, labio 

 dilatato, proteiforme superatum ; anus terminalis ; corpus globulis, laete rubris, 

 internis ubique variegatura. 



5. Aeolosoma venustum. Figs 8 to 12. — Body compressed, colorless, variegated 

 with red spots, broad, proteiforra, of eight articulations, the posterior seven of which 

 are furnished with a pair of infero-lateral fasciculi of setae, each consisting of four, 

 unequal and simple, the longest longer than the breadth of the body, the shortest not 

 equal to the breadth. No setse to the oral segment. Upper lip very large, sub -oval. 

 Anal segment broad, obtusely rounded. Intestine simple, capacious. Generative 

 apparatus ? 



* Gruby, Archiv fiir Naturgeschichte, 1844. B. 1, S. 21 1. 

 t Symbolas Physicae. 



