ART. 3. NEW TREMATODES FROM AMPHIUMA MEANS — CHANDLER. 5 



the latter a circular cleft into which projects a plug. Esophagus 

 opens into oral sucker on ventral side anterior to the pharyngeal 

 pockets, turns jDosteriorly and then dorsally, curving around the pha- 

 ryngeal pockets posteriorl3^ Wall of esophagus thick and muscular, 

 the musculature becoming much thicker near the point of origin of in- 

 testinal ceca, but not forming a sharply defined esophageal bulb. 

 Testes two, very large, globular, one behind the other in middle of 

 ventral part of body. Ovary small, posterior, dorsal. Shell gland 

 immediately posterior to ovary. Laurer's canal opens at level of 

 ovary. Vitellaria in the form of distinct follicles arranged in a 

 curved and largely transverse manner in posterior part of body. 

 (Cirrus pouch small, uterus joining with sperm duct just distal to it, 

 forming a short hermaphroditic duct. No sucker around genital pore. 

 Excretoi-y system opens near posterior end of body on middorsal line, 

 and enlarges into a reservoir posterior to ovary and shell gland. 

 Eggs large, thin shelled. 



Type of the genus. — Megalodiscus am£7'icanus, new species. 



Habitat. — Rectum of Amjjh'mina means, North America. 



The striking characteristics of the genus are the enormous size 

 and peculiar structure of the posterior sucker, the form of the 

 esophagus, the very large size of the testes, which show no tendency 

 toward fusion, and the form and position of the vitelline follicles. 

 In respect to the shape of the esophagus and structure of posterior 

 sucker, Megalo discus is somewhat intermediate between Diplodiscus 

 and Opisthodiscus. It belongs to the subfamily Diplodiscinae as 

 constituted by Cohn (1904). 



MEGALODISCUS AMERICANUS, new species. 



Plate 2, figs. .3-5. 



Body conical, nearly round in cross section, the general shape being 

 not unlike a curved horn with flaring mouth. Length 3.57 mm., 

 with maximum diameter, before flaring out at junction of huge 

 posterior sucker, of about 0.98 mm. Posterior sucker an enormous 

 shallow disk, facing postero-ventrally, 1.7 mm. in diameter, nearly' 

 one and three-fourths times the diameter of the body. Sucker has 

 raised rim and raised center, but in middle of central prominence 

 is a relatively small circular cleft filled with a plug, this structure 

 being reminiscent of the yolk plug of a frog's ^gg (fig. 5). The 

 central plug shows no evidence of a terminal sucker such as is de- 

 scribed by Cohn (1904) for Opisthodiscus. Oral. sucker large and 

 powerful, about 0.45 mm. in depth and 0.28 mm. in diameter at its 

 anterior end. Pharyngeal pockets large and conspicuous, with com- 

 mon median wall, about 0.235 mm. long. Esophagus leaves oral 

 sucker on ventral side, between and anterior to the pharyngeal pock- 



