408 Digenetic Trematodes in Japan 
lateral body margin and reach almost to the posterior end of the body. The 
excretory vesicle is Y-shaped and lies between the intestinal caeca and opens 
at the posterior end of the body. Fhe lumen of the vesicle contains retractile 
excretion granules. At the middle of the body and laterally or dorsallv to the 
intestine are the testes. They lie at the same level. Directly posterior to the 
ventral sucker is a small cell-mass which represents the ovary. 
Exorchis oviformis seem to have a close affinity with Stegopa glohosa Linton, 
which was discovered in the intestine of a marine fish by Linton 1 . The descrip¬ 
tion and the illustration of Stegopa are very incomplete, so I cannot identify 
them. I may add that there is little affinity between the two genera Siphodera 
and Stegopa, which are comprised in one family, Siphoderidae, by Linton. 
(27) Steringotrema nakazawai n. sp. (PI. XXV, fig. 7). 
Diagnosis. Body small, 2-3-3 mm. x 2-2-8 mm.; posterior half broadest. 
Ventral sucker 1 mm. x 1-5 mm. Alimentary canal consists of a spherical 
pharynx, short oesophagus and narrow intestinal caeca which run along the 
lateral margins and end near the posterior end of the body, approaching each 
other at their distal extremities. Excretory vesicle V-shaped, arms reaching 
almost to the oral sucker. Testes entire, round, 0-3—0-4 mm. in breadth. 
Ovary with several lobes, transversely elongated, 0-2 mm. in breadth. Vitel- 
laria consist each of from 5 to 6 groups. Loops of uterus run along the posterior 
and left side of the ventral sucker. Eggs 0-045 mm. x 0-025 mm. Habitat: 
in the intestine of Spams latus. 
Description. This species infests the intestine of Spams latus, and the 
specimens were collected by K. Nakazawa at Taka-no-Shima, Awa Province, 
in 1911. 
Body measures 2-3-3 mm. x 2-2-8 mm. The shape is somewhat ovoidal, 
the posterior half being broadest, and anteriorly it gradually tapers, while pos¬ 
teriorly it ends roundly. The ventral surface is ordinarily flat or concave, while 
the dorsal surface is somewhat convex. In alcohol the specimen is pale blue. 
The cuticle is smooth and relatively thick, being 0-005 mm. The oral 
sucker is situated at the anterior end of the body, and turned towards the 
ventral surface, the diameter being 0-1—0-3 mm. The ventral sucker is very 
large, occupying the main part of the posterior broad part of the body, it is 
broader than long, measuring 1 mm. x 1-5 mm. 
The oral sucker is directly connected posteriorly with the pharynx, with¬ 
out the intervention of a prepharynx. The pharynx is 0-2 mm. x 0-2 mm. 
A short oesophagus is present. Its length is 0-2 mm. The intestinal caeca run 
along the borders of the ventral sucker, as far as the posterior border of the 
latter, and end near the median line. The lumen of the intestine is relativelv 
narrow. 
Excretory vesicle V-shaped, and opening on the dorsal surface near the 
1 Linton, E. (1910). Helminth fauna of the Dry Tortugas. II. Trematodes. Publication 
No. 133, Carnegie Institution. 
