No. 5 meserve: monogenetic trematodes 49 



parallel rows. Posterior suckers elliptical, wider than long, anterior 

 pair smaller, 0.048 to 0.060 mm. in length by 0.060 to 0.068 mm. in 

 width; other three pairs 0.056 to 0.068 mm. in length by 0.068 to 

 0.080 mm. in width. Chitinous skeleton (fig. 27) of four pieces, 

 central piece heavy, very broad, bifurcated and blunt posteriorly, 

 bifurcated anteriorly with two sharp points which are recurved, 

 sharply pointed, pointing toward base of sucker; two pairs of lateral 

 pieces, heavy, uniting posteriorly; an anterior piece horizontally 

 across top of sucker with ends bent slightly and pointing toward 

 base of sucker. Two pairs of hooks at posterior end of body between 

 posterior pair of suckers. Outer pair extremely large and stout, 0.100 

 to 0.132 mm. in length, solid with sharp, recurved points, opposite 

 ends (anterior roots) truncate, anterior root one third distance from 

 distal end; proximal half of hook deeply grooved on its surface. 

 Inner pair hooks approximately one sixth length of larger pair, 0.02 

 mm. in length, filiform, with sharp recurved points, possessing a 

 process about one third the distance from the distal end, posterior 

 end of hook slightly turned up at end. Each sucker with skeletal 

 apparatus of four pieces. Mouth subterminal, ventral. Anterior 

 mouth suckers large, elliptical, broader than long, without mem- 

 branous septa. Pharynx bulb-shaped, near anterior suckers, slightly 

 longer than wide. Esophagus relatively long, slender, bifurcating 

 approximately one half distance from anterior end of animal to 

 ovary. Intestinal limbs extend posteriorly to anterior end of posterior 

 pair of suckers, not united posteriorly, with lateral branches. Cirrus 

 consists of central bulb-shaped body 0.052 to 0.064 mm. in diameter. 

 Two lateral bean-shaped bodies of cirrus longer than wide, 0.048 

 mm. in length. Five pairs of cirrus hooks, one pair of stout, long 

 hooks with broad bifurcated bases and sharp slightly curved points, 

 and four pairs of smaller inner hooks which have bulb-shaped bases 

 and taper gradually from the proximal to distal ends and are slightly 

 curved from base to point. Testes large, few in number (ten), 

 smooth, unlobed, broader than long and angular, to right of and 

 posterior to ovary in anterior part of posterior half of animal. Genital 

 pore in mid-line near anterior end, about one half the distance from 

 anterior end of animal to bifurcation of esophagus. Ovary in middle 

 of body to left of mid-line, U-shaped with open end of U pointing 

 anteriorly, both arms approximately the same length and of uniform 

 diameter throughout. Oviduct leaves anterior part of right arm of 



