Monogenetic Trematodes, I — Yamaguti 
diately dextral to distal portion of ovary. 
DISCUSSION : This obviously gastrocotylid spe- 
cies cannot be assigned to any known genus on 
account of absence of a vagina and peculiar 
arrangement of the testes. A new genus and a 
new subfamily are, therefore, proposed for its re- 
ception, referring to the areolate testes. 
Areotestiinae n. subf. 
SUBFAMILY DIAGNOSIS: Gastrocotylidae : 
Clamps unilateral, symmetrical in structure, with 
accessory sclerites. Hook-bearing caudal appen- 
dage present, prehaptoral larval anchors absent. 
Testes divided into numerous groups which are 
isolated one from another by anastomosing in- 
testinal branches. 
Areotestis n. g. 
GENERIC DIAGNOSIS: Gastrocotylidae, Areo- 
testiinae: Haptoral clamps nearly of G astro co- 
tyle type, arranged along straight or arcuate 
posterior margin of body, the distal end of which 
is produced into a terminal lappet bearing 2 
pairs of anchors. Esophagus simple, long; in- 
testinal limbs with numerous branches anas- 
tomosing one another in form of extensive 
network. Testes divided into numerous areolae 
of different size and outline and enclosed in 
meshes of this intestinal network. Pars pro- 
statica distinct, surrounded by prostate cells. 
Genital atrium muscular, provided inside with 
a crown of hooks, enclosing armed bulbous cir- 
rus, opening ventral to esophagus. Ovary folded 
back on itself in posterior interintestinal field, 
with both ends directed backwards. Genito- 
intestinal duct short, frequently forming rounded 
or elongate seminal receptacle. Eggs fusiform, 
produced into rigid processes at both ends. 
Vagina absent. Vitellaria co-extensive with in- 
testine and its network, some follicles extending 
forwards along esophagus; vitelline reservoir in 
ovarian zone. Gill parasites of marine teleosts. 
TYPE SPECIES: A. sibi n. sp., on gills of Para- 
thunnus sibi , Neothunnus macropterus, and 
Thunnus alalonga; Hawaii. 
18. Allomicrocotyla onaga n. g., n. sp. 
Fig. 18 
91 
HABITAT: Gill of Etelis carbunculus (local 
name "onaga” ); Hawaii. 
HOLOTYPE: U. S. Nat. Mus. Helm. Coll., S.Y. 
No. 18. 
DESCRIPTION ( based on five whole mounts ) : 
Body proper fusiform to elliptical; opisthohap- 
tor shaped like an asymmetrical fan fringed 
with two rows of clamps along its semicircular 
posterior margin which is 0.8-1. 4 mm long. At 
one end of the opisthohaptor there are two pairs 
of anchors of different size and shape. Total 
body length 2. 5-4.0 mm, maximum width 0.8- 
1.6 mm in midregion of body proper. Clamps 
40-63 in number, arranged in two rows of equal 
or subequal length, 20-31 in one row and 20-33 
in the other; clamp skeleton of uniform struc- 
ture, consisting of a basally jointed median 
spring, two pairs of unjointed lateral arms, and 
a pair of basal sclerites, each of which articulates 
with the base of the two lateral arms at one end 
and with the enlarged end of dorsal prong of 
the median spring at the other end; the narrow 
solid ventral prong tapers toward its bifid tip 
reaching the tips of the ventral lateral arms, 
while the short dorsal prong curves ventrad and 
terminates in a transversely enlarged solid pad 
which is united by muscle with another ven- 
trally curved hollow median sclerite reaching to 
tip of dorsal lateral arms. Head more or less 
pointed anteriorly, 0.11-0.13 mm wide at level 
of oral suckers; at the apex is a compact group 
of gland ducts originating from the group of 
parapharyngeal, postsuctorial gland cells and 
passing dorsal to the oral suckers. I prefer to 
designate the apical group of gland ducts as 
apical organ, and the parapharyngeal mass of 
gland cells as apical gland, although the struc- 
tural details of the gland cell could not be made 
out except for the granular cytoplasma surround- 
ing the dark-staining nucleus which is definitely 
larger than the adjoining parenchymatous nuclei. 
Mouth comparatively wide, opening ventrally at 
level of base of head. Oral suckers opening into 
buccal cavity, one on each side of anterior end of 
pharynx, strongly muscular, aseptate, 40-55 /a by 
50-56/a. Pharynx pyriform, 37-65 X 32-51/a, 
cellular except at the apex which is provided 
with circular muscle fibers. Nerve commissure 
FIG. 17. Pseudochauhanea sphyraenae n. g., n. sp. 17 A, Holotype, ventral view; 17B, clamp; 17 C, terminal 
genitalia; 17 D, vagina and its accessory ducts. 
