396 PROCEEDINGS OF THE NATIOyAL MUSEUM. vol.46. 



like point is slightly incurved and no doubt immovably united to 

 the rami. 



The stomach is without separate intestine; the ovary, contractile 

 vesicle, and foot-glands are normal. 



Total length, 160 «; toes, 26 fi; trophi, 24 fi. 



Type. — Cat. No. 16518, U.S.N.M., comes from Kenilworth, Dis- 

 trict of Columbia, where the species occurs in small numbers among 

 the branches of Myriophyllum. 



ENCENTRUM RICCI^, new species. 

 Plate 34, figs. 4-6. 



The body tapers gradually toward the foot, which is short and 

 sharply marked off, with a tail projecting over it dorsally; a promi- 

 nent triangular ligula overarches the corona. The toes are cylindric 

 and of the same diameter throughout their length, straight at the 

 base, and strongly decurved posteriorly; the ends are rounded. 



The oblique corona has two fairly prominent auricles at the base 

 of the hgula. The gangUon is moderate-sized and closely overlaid by 

 the rather small retrocerebral sac ; no subcerebral glands have been 

 found, nor are any eyespots present. 



The hexagonal cells of the stomach are conspicuous; the functions 

 of an intestine are apparently performed by the posterior third of the 

 stomach, although not separated from it by any constriction; its 

 walls do not show the cell divisions. Ovary and contractile vesicle 

 are normal, the foot-glands fairly long and nearly cyhndric. 



The trophi are forcipate and, whUe not aberrant, are quite charac- 

 teristic. The iimer edges of the rami are nearly semicircular; a long, 

 curved, needlelike tooth passes abruptly into the irregularly triangu- 

 lar posterior section. The fulcrum is rodlike, its extreme end 

 shghtly recurved. The manubria are strongly curved, their upper 

 ends forked, embracing the exterior edges of the rami; the unci are 

 divided into an uncus proper and a long, curved tooth. A relatively 

 considerable space separates the unci from the manubria and their 

 original relation has been completely lost, the unci acting merely as 

 a second tooth to the rami, to which they are immovably united by 

 muscular bands, at the base of the tooth further reenforced by a 

 small V-shaped member, resting with one branch on the ramus, the 

 other on the tooth. The manubrise have become simple auxiharies 

 to the rami; their form makes it obvious that the adductor muscles 

 of the rami are attached to them, thereby efi'ecting the closing move- 

 ment, the crutch of the manubria being united to the triangular 

 alulae by flexible ligaments. 



Total length, 190 //; toes, 22 fi; trophi, 31 n. 



This species was found in the fall among clumps of Riccia Jiuitanc 

 in ponds at Kenilworth, District of Columbia. Apparently it does no»t 



