FREE-LIVING FRESH-WATER NEMATODES 47 



derived from a single specimen in which these features are rather obscure. 

 The reversal in the striations of the cuticle is plainly to be seen in the re- 

 gion of the vulva, and its location is indicated by a slight rise in the contour. 

 This slight elevation extends also to the subcuticle. 

 60 



.5 8.3 14.8 -M 88.4 



.7 mm. 



2. 4.3 4.7 5. 3.2 



The wing markings on the anterior part of the tail are pronounced, 

 but on the posterior part much less so. A little in front of the 

 anus they are as pronounced as they are at the base of the 

 neck, and both are equally visible, and the structure not infrequently re- 

 sembles that of a ladder with the rungs placed close together, just as it does 

 on the neck. The lateral fields appear to be about one-third as wide as the 

 body. Near the middle of the body may plainly be seen the location where 

 the cuticle reverses its structure. Although the striations are minute they 

 present the same character as in species where the striations are coarse, and, 

 upon careful examination, can be seen to be retrorse in opposite directions 

 on the two halves of the body. 



Habitat : Fresh water ponds, Cape Breton Island, Dominion of Canada. 



MICROLAIMUS, de Man, 1880. 

 Fig. 6, Plate III. 



27 



6. Microlaimus fluviatilis, n.sp. *- 6 8 -5 *5-5 V 85. mm 



1-9 3-5 4-3 47 2.6 



The thin layers of the transparent, colorless, naked cuticle are traversed 

 by exceedingly fine transverse striae, which are resolvable with great diffi- 

 culty into rows of dots, and are not modified on the lateral fields. The 

 conoid neck ends in a rounded head set off by an almost imperceptible con- 

 striction. On the outer margin of the head there is a circlet of four sub- 

 median, slightly tapering cephalic setae, each about one-third as long as the 

 head is wide. The vestibule is considerably shorter than any of the cephalic 

 setae, and is longitudinally striated, indicating, no doubt, that the lips can 

 be opened outward in receiving food. These longitudinal striations of the 

 vestibule are too minute to be counted, but there are apparently about twelve. 

 The circular amphids are about one-fourth as wide as the corresponding 

 portion of the head, and are located at a distance from the anterior ex- 

 tremity equal to one and one-half times the diameter of the front of the 

 head. There are no eye-spots. The limits of the pharynx are indicated by 

 a slight constriction in the oesophagus. The base of the pharynx is some- 

 what more than halfway back to the amphids. The general form of the 

 pharynx is cylindroid or prismoid. It is armed with minute and very in- 

 conspicuous, somewhat inward pointing and apparently not very regular 

 teeth or projections. The most conspicuous of these projections are two just 

 behind the base of the lips, one dorsal and the other apparently ventral, and 



