552 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.46. 



are flattened under a cover glass. The head is surrounded with a 

 collar on which is a row of spines which vary but little m size from 

 those which thickly beset the neck as far back as the ventral sucker. 



Dimensions of a living specimen, in millimeters: Length, 6.2; 

 breadth, 4; diameter of head 1.20, of oral sucker 0.42, of pharynx 

 0.22, of ventral sucker 1.18; small ova, i. e., those in posterior folds 

 of uterus and not containing ciliated larvae, 0.08 by 0.04; large ova, 

 i. e., those in anterior folds of uterus, each containing a ciliated larva 

 with a black pigment spot, 0.12 by 0.07. 



Measurements of ova in another specimen yielded nearly similar 

 dimensions, thus: Ovum not containing larva 0.085 by 0.041 ; ovum 

 containing larva 0.136 by 0.071. 



The following description is based, for the most part, on specimens 

 stained with carmine and mounted in balsam. 



General outline oval or pjTif orm, but more or less distinctly divided 

 into head, neck, and body. Head differentiated from the neck by a 

 muscular collar which projects distinctly laterally and apparently 

 ends abruptly on the ventral side at the margins of the oral sucker, 

 but really passes by a very indistinct fold across the ventral surface 

 of the oral sucker (fig. 3). 



A single row of small spines was seen on the collar of living speci- 

 mens; spines of similar shape and slightly smaller are numerous on 

 the neck but occur sparingly on the body back of the ventral sucker. 

 The spines are short, round-pointed, and scalelike (fig. 6). They are 

 not at all conspicuous in the mounted specimens. The neck extends to 

 about the level of the ventral sucker. The body proper, that is the 

 portion lying posterior to the middle of the ventral sucker, is round- 

 oval and leaf-like. It is flattened or concave on the ventral surface 

 and convex on the dorsal surface. The neck has a tendency to curve 

 ventrall}^. Suckers nearly circular or a little broader than long with 

 nearly circular apertures, oral sucker subterminal. Ventral sucker 

 rather more than twice the diameter of the oral and situated at about 

 the anterior third, the distance between the two suckers being ap- 

 proximately one-fiith of the entire length. Pharynx adjacent to the 

 oral sucker oval, its length about half the diameter of the oral sucker, 

 Pre-pharynx very short. Esophagus approximately twice the length 

 of the pharynx, its walls more or less crumpled and irregular in out- 

 line (fig. 4). Intestinal rami beginning a short distance in front of 

 the ventral sucker, slender and without diverticula, extending to 

 near the posterior end of the body, where they lie close to the lateral 

 borders of the testes. The reproductive aperture lies immediately 

 in front of the ventral sucker, the space between the anterior border 

 of the ventral sucker and the rami of the intestines being nearly filled 

 by the prostate which surrounds the genital aperture. Testes two, 

 deeply lobed, near the posterior end of the body, close together and 



