192 PROCEEDINGS OF THE NATIONAL MUSEUM vol.84 



terminal, slightly more muscular than acetabulum, transversely oval, 

 0.15 mm long by 0.1 G mm wide. Acetabulum 0.105 mm long by 0.122 

 mm wide, about one-third body length (0.42-3 mm) from anterior end. 

 Ratio of sizes of oral sucker and acetabulum, approximately 3:2. 

 Pharynx muscular, transversely oval, 0.033 mm long by 0.068 mm 

 wide, connected with oral sucker by short prepharynx, surrounded 

 by numerous peripharyngeal gland cells. Esophagus slightly longer 

 than transverse diameter of pharynx, surrounded by periesophageal 

 gland cells. Caeca saclike, rather long, 0.17 mm long by 0.074 mm 

 wide, ending well in front of acetabulum, lined internally with rather 

 low epithelial cells. Ovary almost spherical, 0.091 nun long by 

 0.10 mm wide, alternating from right to left side of acetabulum, 

 usually about on same level as acetabulum. Oviduct delicate, long. 

 Ootype at about level of equatorial plane of acetabulum. Laurer's 

 canal present. Shell gland surrounding ootype. Receptaculum 

 seminis spherical, large. Uterus a simple tube, descending to near 

 posterior margin of body by a series of transverse loops, ascending 

 by similar course to genital pore; loops almost completely crossing 

 body in posttesticular region of body. Ova 27)it to 30/a by 39;li to 45/x, 

 thick-shelled, operculated, fully embryonated when oviposited. Met- 

 raterm weakly developed. Vitellaria sparse, follicles spindle-shaped, 

 widely separated, forming a continuous bridge under dorsal surface 

 just posterior to bifurcation of caeca; vitellaria in lateral fields, 

 extending from anterior margin of ovary on one side and anterior 

 margin of testis on other side to level of bifurcation of caeca. Yolk 

 ducts converging near ootype to form small yolk reservoir. Testes 

 transversely oval, behind level of acetabulum, opposite or slightly in 

 tandem, depending on position of ovary for their exact location 

 (when ovary is right, right testis more posterior) ; right testis 0.109 

 mm long by 0.141 mm wide; left, testis 0.156 mm long by 0.153 mm 

 wide. Vasa efferentia uniting on entering cirrus sac. Cirrus sac 

 club-shaped, usually forming an inverted U just in front of acetab- 

 ulum, but sometimes lying dorsal or lateral to acetabulum, rarely 

 extending to posterior margin of sucker, containing spherical vesicula 

 seminalis, bulbous pars prostatica with its gland cells, a short ductus, 

 and a weakly developed cirrus. Excretory system identical with 

 that of other members of the genus, with a flame cell pattern of 

 the 2X6X3 type. 



Host. — Amby stoma opacum (Gravenhorst). 



Habitat. — Small intestine. 



Locality. — ^Pearl River, La. 



Tyj)e speciinen. — U.S.N.M. Helm. Coll. no. 9029. 



Remarks. — Brachycoelium dorsale appears to be more closely re- 

 lated to B. stoferiae than to any of the other members of the genus. 

 It is separated from this species by the extent and configuration 



