350 [December, 



lateral respiratory foveae of the head are, according to him and other authors, 

 ocelli destitute of pigment. 



In numerous individuals of what I have considered below to be of three dis- 

 tinct species of the genus, they were always observed to be in a state of division 

 by pairs, and the primary pair of segments about their middle had already 

 developed respiratory foveae, and were slightly indented preparatory to division 

 before the first pair were separated. 



1. MicRosTOMUM (Eustomum'^ Philadelphicum, Leidy. 



Body linear, slightly attenuated posteriorly ; head conoidal^ with the apex 

 surmounted by a small oval papilla ; tail obtusely rounded. Respiratory fovea 

 sub-hemispherical, placed at the base of the cone of the head. Mouth oval, pro- 

 tractile ; (Esophagus keg-shaped, intestine narrowed, cylindroid, dilated at the 

 commencement. Colorless, translucent, vibrillated ; Increasing by transverse 

 segmentation, always observed in the process of forming two segments. 



Length 2-5ths line, by l-500th in. broad. 



Habitation. Found in the water of marshes and ditches in the neighborhood 

 of Philadelphia. 



2. MiCROSTOMUM {Eustomum') variabile, Leidy. 



Body broad, linear ; anteriorly and posteriorly obtusely rounded. Respiratory 

 fovea, longitudinally oval, lateral. Intestine very broad. Colorless, increasing 

 by twos. 



Length from 1.80th to' 1. 24th of an inch by 1.800th to 1.400th in. 

 broad. 



Habitation. With the preceding. 



3. MicRosTOML'M (Eustomurn\ caudatum, Leidy. 



Body long, narrow, linear ; anteriorly obtusely rounded, posteriorly ending 

 in a narrow, blunt, elevated tail l-400th in. long from the position of the anus; 

 increasing by twos, the tail of the anterior segments projecting above and its 

 whole length posterior to the head of the succeeding segment. 



Length 3-4ths to 1^ lines; breadth l-SOOth to the l-250th in. 



Habitation. With the preceding. 



Rhynchodemus stlvaticus, Leidy . Pr. A. N. S. v, 289. Error of reference. 

 Planaria sylvatica, Leidy: ib. 241. 



Stylaria fossularis Leidy: ib. 287. A number of individuals in a state of 

 segmentation, from which the species was first described, preserved alone in a 

 glass vessel with some confervjE, upon the occurrence of cold weather passed 

 into the perfect condition as follows : 



Body long, cylindroid, hyaline, permitting the ash-colored or yellowish intes- 

 tine to be seen through the integument, divided into from 50 to 65 annulations, 

 furnished with a distinct girdle posterior to the third annulus from the mouth, 

 which extends the breadth of three annuli. Podal hooks in fasciculi of 10 to 

 12. Setae commencing after the girdle, usually one often two upon each side 

 of the annuli. Head obtusely rounded and prolonged into a cylindroidj very 

 moveable, digitiform, transversely wrinkled proboscis. Caudal annulus termi- 

 nating in two short lobes 



