40 



BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



Morphology. — Syngamus (p. 34) : Superficially (fig. 44) resem- 

 bling S. trachea but smaller and more slender. 



Male 3 to 3.3 mm. long by 270/* wide. Buccal capsule 165/* deep 

 by 200/* wide near the anterior edge; wall 45/* thick. Buccal teeth 

 as in JS. trachea, the largest 45/* high. Esophagus nearly 600/* long, 

 clavate, its greatest diameter 135/*. Nerve ring, excretory pore, and 

 cervical papillae not seen. Bursa (fig. 45) narrow an\l deep. As 

 in JS. parvus, the dorsal ray branched, the branches simple ; however, 

 whereas in JS. parvus the bifurcation is only near the tip, in the 

 present species the bifurcation is basal, resulting in a total suppres- 

 sion of the common dorsal trunk, the branches being 150/* long. 

 Externo-dorsal ray slightly shorter, measuring 132/*. Lateral rays 

 mutually contiguous, parallel, and about the size of either branch 



WOju 



Figs. 44-46. — Syngamus gracilis. 44, Male and antekiok 

 portion of female. 45, male- bursa. 46, female tail. 

 After Chapin, 1925 



of the dorsal ; ventral rays smaller and more slender. Spicules dis- 

 tinctly unequal; the right, 79/* long, is bent, the left, G9/* long, is 

 nearly straight. 



Female 8 to 11 mm. long and proportionately stouter than the 

 male. Buccal capsule relatively enormous, its internal dimensions 

 525/* wide by 300/* deep ; wall 50/* thick. Teeth as in JS. trachea. 

 Esophagus 825/* long, attaining its greatest diameter, 225/t, near its 

 posterior end. Vulva 1.4 mm. from anterior end, or at about the 

 anterior eighth of body length. Vagina longer than in related 

 species; uteri parallel, posteriorly directed. Anus (fig. 46) about 

 300/* from posterior end, which is very blunt. Eggs 79 to 83/* by 

 40 to 46/*. 



Life history. — Unknown; probably similar to that of S. trachea 

 (p. 36). 



Distribution. — North America (Philadelphia Zoological Park). 



Chapin has noted that in all probability it is this species that has 

 formerly been found in the American crow and reported as JS. 



