Digenetic Trematodes, I — YAMAGUTI 
481 
men 32 mm long, but in the longest specimens 
(48 mm) it lies anterior to the midbody divid- 
ing the body in ratio of 21:27. Seminal recep- 
tacle oval, 100 X 80 jx in the type, situated 
dorsal to this point of genital junction. De- 
scending uterine duct surrounded by shell gland 
for a length of about 0.4 mm in the type, turn- 
ing forward in the type across median line from 
one side to the other at a distance of 0.9 mm 
from posterior extremity; this ascending uterine 
limb turns across the median line once more 
3.3 mm posterior to the head end to take an 
exactly identical descending course on the op- 
posite side and passes into the final ascending 
limb 0.55 mm from the posterior extremity; 
thus the entire uterus forms three loops, one at 
a short distance from the head end and two near 
the posterior extremity; distal portion of final 
ascending uterine limb differentiated into mus- 
cular metraterm which runs forward nearly in 
the median field along with the vas deferens; 
eggs bean-shaped, 14-21 X 7.5-12 /x. Vitella- 
rium narrow, tubular, strongly twisted through- 
out. In the type it originates 0.2 mm from 
posterior end of body and runs forward medial 
to proximal ascending uterine limb opposite 
testes. Excretory vesicle tubular, somewhat 
winding in median field, its anterior termina- 
tion not made out; excretory pore terminal. 
DISCUSSION: This genus bears a certain re- 
semblance to Allometanematobothrioides , espe- 
cially in that the uterus makes three U-turns 
( though turning first near the posterior extrem- 
ity instead of posterior to the ovary), and in 
the intestinal limbs being very narrow and very 
strongly convoluted, and in the anterior extrem- 
ity markedly tapering. But the two genera differ 
fundamentally in the structure of the esophagus. 
N e o ne mat oboth riu m n. gen. 
GENERIC DIAGNOSIS: Didymozoidae, Nema- 
tobothriinae. Body long, slender, flattened, 
markedly tapered anteriorly. Oral sucker and 
pharynx rudimentary. Esophagus unusually long, 
with numerous diverticles surrounded by gland- 
ular cells, bifurcating in midregion of body into 
unequal branches, each of which passes into a 
very narrow, convoluted cecum terminating 
near posterior extremity. Acetabulum absent. 
Testes narrow, twisted, parallel to each other 
for the most part, originating at different levels; 
posterior testis largely in greater posterior por- 
tion of body. Genital pore ventral, postpharyn- 
geal. Ovary single, tubular unbranched, orig- 
inating at level of anterior U-turn of uterus or 
further behind it. Seminal receptacle present. 
Uterus first descending to near posterior ex- 
tremity, then ascending and turning backward 
a short distance back of anterior extremity, 
forming another U-turn near posterior extrem- 
ity before taking its final ascending course; eggs 
bean-shaped, small. Vitellarium single, narrow, 
tubular, extending between ovary and posterior 
extremity. Excretory vesicle with terminal pore, 
probably bifurcating anteriorly. Parasitic, free 
in subcutaneous tissues of opercular region of 
marine teleosts. 
type species: N. kawakawa n. sp., in Eu- 
thynnus yaito; Hawaii. 
REFERENCES 
Ishii, N. 1935. Studies on the family Didymo- 
zoidae (Monticelli, 1888). Jap. J. Zool. 6 
(2 ) : 279—335. 
Manter, H. W., and M. H. Pritchard. I960. 
Some digenetic trematodes of eels of Hawaii. 
J. Parasitol. 46 ( 5 ) : 65 1-658. 
Nagaty, H. F. 1942. Trematodes of fishes from 
the Red Sea. III. On seven new allocreadiid 
species. Publ. Mar. Biol. Sta. Ghardaqa (Red 
Sea) , No. 4, 27 pp. 
Odhner, T. 1905. Die Trematoden des ark- 
tischen Gebietes. Fauna Arctica 4(2) : 291— 
372. 
Yamaguti, S. 1958. Studies on the helminth 
fauna of Japan. Part 52. Trematodes of fishes, 
XI. Publ. Seto Mar. Biol. Lab. 6(3): 369-384. 
1958. Systema helminthum. Vol. I. The 
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