Trigonocryptus conus — Martin 
253 
average 0.44 anteroposteriorly and 0.41-0.55, 
average 0.48 transversely. Ventral sucker large, 
muscular, indented anteriorly and posteriorly, 
with two or three transverse ridges, 0.45-0.59, 
average 0.52 anteroposteriorly and 0.64-1.02, 
average 0.86 transversely. Prepharynx short, 
pharynx 0.093-0.112, average 0.10 anteropos- 
teriorly and 0.081-0.121, average 0.11 trans- 
versely. Esophagus short, ceca thin walled, 
short, saccular, not extending beyond body 
equator. Testes near posterior end of body, 
opposed, oval, 0.17-0.28, average 0.22 long 
and 0.14-0.21, average 0.17 wide. Vasa ef- 
ferentia join just before reaching cirrus sac. 
Cirrus sac median, immediately anterior to or 
partially overlapped by acetabulum, contain- 
ing weakly bipartite seminal vesicle filled with 
sperm, a well-developed prostate, and a short 
cirrus which may project into the genital 
atrium. Genital pore median and ventral at 
level of gut bifurcation. Ovary median, usu- 
ally a short distance anterior to testes, 0.096- 
0.17, average 0.15 long and 0.084-0.15, aver- 
age 0.12 wide. Seminal receptacle pyriform, 
usually a short distance posterior and to the 
right of the ovary. Mehlis gland close to 
ovary, inconspicuous. Vitelline follicles in two 
major clusters on each side of body between 
anterior acetabular and oral sucker levels. 
Common vitelline duct not expanded to form 
reservoir. Uterus after leaving ovary passes 
posteriad to loop between the testes then ex- 
tends anteriad to loop transversely and fill 
much of the acetabular region of the body. It 
then passes anteriorly to the genital atrium. 
The uterus of mature worms is filled with 
eggs. Newly formed eggs colorless, older 
eggs brown. Eggs 0.037-0.046, average 0.041 
long and 0.022-0.025, average 0.023 wide, 
operculated, with a small knob at anopercular 
end. Excretory vesicle U-shaped, thin walled, 
with pore opening medially and subterminally. 
type specimen: Trigonocryptus conus, depos- 
ited as number 55285 in the U. S. National 
Museum, Helminth Collection. 
HOST: Tetraodon hispidus L., balloon fish, 
in intestine. 
locality: Kaneohe Bay, Oahu, Hawaii. 
DISCUSSION 
The genus Trigonocryptus most closely re- 
sembles Paradiscogaster Yamaguti, 1934. The 
major difference is in the vitellarian distribu- 
tion, in one cluster on each side of the body 
confined to the cecal region in Paradiscogaster , 
and in two clusters on each side of the body 
extending from the acetabulum to the oral 
sucker in Trigonocryptus. Other differences are 
the ventrolateral extensions of the oral sucker 
in Trigonocryptus while this organ in Paradis- 
cogaster has the usual circular outline; the un- 
usual body shape in Trigonocryptus with a 
ventral, triangular depression, a velum on the 
lateral and dorsal margins of the posterior 
part of the body, and a truncated posterior 
end while the body shape is pyriform in Para- 
discogaster. Yamaguti (1938) described a small 
tail cone in Paradiscogaster chaetodontis. Trigo- 
nocryptus conus has an inverted tail cone, dorsal 
to the excretory pore, which was never seen 
everted even in active worms. Paradiscogaster 
piriformis Yamaguti, 1934, was found in 
Pleuronichthys cornatus in Japan (Yamaguti, 
1951); P. chaetodontis Yamaguti, 1938, in 
Chaetodon collaris in Japan and C. strigangutus 
and C . trifasciatus in Okinawa (Yamaguti, 
1953); and P. caranxi (Srivastava, 1939) Ya- 
maguti, 1953, in Caranx kalla in India. Al- 
though a goodly number of Hawaiian chaeto- 
dons and a few carangids have been examined, 
no species of Paradiscogaster or Trigonocryptus 
have been found in them. Hanson (1955) has 
reported a related form, Discogasteroides ha- 
Figs. 1-5. Trigonocryptus conus: 1, Dorsal view; 2, ventral view; 3, egg; 4, body spine; 5, terminal genitalia. 
A, Acetabulum; C, cecum; Ci, cirrus; CS, cirrus sac; EV, excretory vesicle; G, genital pore; O, ovary; OS, oral 
sucker; P, pharynx; PR, prostate; S, seminal receptacle; SV, seminal vesicle; T, testis; U, uterus; V, vitellaria; 
V, velum. All drawings made with the aid of a camera lucida. 
