46 



BULLETIN 140, UNITED STATES NATIONAL MUSEUM 



diameter. Esophagus 730/* long, clavate, its diameter 74//, at the 

 anterior end, 130/x at the posterior end ; nerve ring at the middle of 

 the length, cervical papillae at about posterior seventh of esophagus, 

 excretory pore just anterior to beginning of intestine. Bursa (fig. 

 61) well developed, 750/x in transverse diameter when outspread. 

 Ventral rays similar and approximate; externo-lateral shorter than 

 other lateral rays and with a prominent ventral hump ; medio-lateral 

 and postero-lateral rays similar and approximate; externo-dorsal 



Fig. 59. 



-Cl'ATHOSTOMA AMERICANUM. OUTLINE OF FEMALE AND MALE WORMS. 

 CHAPIN, 1925 (a> = EXTENT OF UTERI) 



After 



ray more slender than, but equal in length to, the externo-lateral ray, 

 arising at the base of the dorsal ray. Dorsal ray divided near its 

 extremity into 2 simple branches. Spicules filiform, equal, from 470 

 to 490/x long, united at their tips and each bearing a finely striated 

 wing. 



Female up to 30 mm. long; similar in form (fig. 59) to the male. 

 Buccal capsule (fig. 60) much broader than deep, its internal 

 transverse diameter 370/i, the depth of its chitinous portion 280/x; 



Fig. 60. — Cyathostoma americanum. Head, a, Side view, male ; b, 

 front view ; c, side view, female. After Chapin, 1925 



wall 20/t thick. Buccal teeth shorter and blunter than in male; 

 largest tooth 60/x high. Head papillae as in male, slightly more 

 anterior in location. Esophagus 960/i long, clavate, its diameter 130/x 

 at anterior end, 250/x at posterior end ; nerve ring at middle of length, 

 cervical papillae opposite the thickest portion of esophagus, excre- 

 tory pore near its posterior end. Vulva (fig. 62fr) just anterior to 

 middle of body, its lips prominent. Anus (fig. 62c) just anterior 

 to slender caudal appendage. Eggs (fig. 62a) 72/t by 42/x, thin 

 shelled, with a small operculum at one pole. 



