70 RESEARCHES IN HELMINTHOIvOGY AND PARASITOLOGY. 



Ordinary length from i to 6 lines; breadth from i-8th to r-5th 

 line. Occasionally lo lines long by i-3d broad. 



Habitatio)i. — In marshes, ditches, and stagnant ponds in the vicin- 

 ity of Philadelphia. 



J'ariefy a. — White, 2 lines long ; i-6th line broad. 



Habitation. — On the under side of stones in the Schuylkill river. 



Remark. — I have sometimes met with the largest sized females 

 without the appearance of a developed ovum, and at others, those 

 of from I to 3 lines in length, with from 3 to 1 8 large yellow eggs. 



2. Emea Diigesii, Leidy. 



Polia Diigcsii, Quatrefages. Rech. Anatom. et Zoolog., ii, 211. 



Dendkocoklum, Oersted. 



Characters same as Planaria, with the head furnished with a 

 hemispherical cotyloid cavit3^ capable of eversion into the form of 

 a pediculated discoidal acetabulum. 



I. Dendrocoeliuu Superbuin , Girard. Proc. Bost. vSoc. Nat. Hist., 

 iii, 265. Keller and Tiedemann, Nordamerik. Monatsb., ii, 2, 



Body thin, plano-convex, translucent white, with the sides nearly 

 parallel ; anteriorly truncated, with the lateral angles slightly pro- 

 jecting ; posteriorly obtusely angular. Cotyloid cavity of the head 

 prominent, opening at the anterior truncated margin, when everted 

 presenting the form of a circular disk supported upon a broad co- 

 lumnar contraction of the head. Eyes two, nearly globular, com- 

 posed of a transparent vitreous humor enclosed at the postero-internal 

 half by a black choroid. QBsophagus long, keg-shaped ; intestine 

 delicately and minutely ramified, brown or blackish-brown in color. 



Length 3 to 8 lines ; breadth 2-5ths to 4-5ths of a line. The 

 longest ma}^ contract to 3 lines to 4-5ths in breadth. 



Habitation ajid Remarks. — In ditches communicating with the 

 Delaware and Schuylkill rivers, below Philadelphia, creeping upon 

 the submerged stems of Arum virginicum, Pontedcria eordata, Nelum- 

 bium /iiteum, and Zizania aguaftca. 



When seized or irritated it everts its acetabulum, bj^ which it at- 

 taches itself to surrounding bodies with the tenacity of a leech. 



Rhvnchodemus, Gents novum. 



Body cylindroid, ob-fusiform. Head continuous with the bod 5', 

 proboscidiform, recurvatile, without tentacular appendages. Eyes 

 two lateral. Interior structure planaroid. Terrestrial. 



I. Rhynchodcmus Sylvaticus, Leidy. Pr. A. N. S., v, 241. 



