NO. 14 MANTER : DIGENETIC TRERIATODES OF FISHES 433 



Eggs without filaments. Excretory pore ventral, excretory crura uniting 

 near oral sucker. Type species: T. fustiforme Linton, 1910. 



This genus is to be classified in the subfamily Derogeninae. 



T. lissosomum is very clearly distinct from T. fustiforme. Among the 

 differences are : sucker ratio 2 :3 rather than 1 :2, more anterior ovary, 

 smaller sinus sac, larger prostatic gland, less coiled and smaller seminal 

 vesicle. 



Although the two species occur in different oceans, both occur in 

 angelfishes. 



Theletrum gravidum, new species 

 (Plate49, figs. 122, 123) 



Host: Abudefdtif saxatilis (Linn.) 



Location : Usually in the stomach, sometimes in the intestine 



Localities: Socorro and Clarion islands, Mexico 



Number : Collected from 4 hosts ; 2 to 5 specimens in each host 



SPECIFIC DIAGNOSIS OF THELETRUM GRAVIDUM 



Body smooth, cylindrical, rounded at each end, somewhat more taper- 

 ing at anterior end, posterior end usually broadly rounded, 1.566 to 2.443 

 in length by 0.465 to 0.667 in greatest width. Forebody 0.405 to 0,547 

 or about 1-4 to ^ body length. Oral sucker subspherical, 0.150 to 0.202 

 in diameter. Acetabulum 0.262 to 0.375 in transverse diameter, slightly 

 longer than wide, slightly less than twice diameter of oral sucker, with 

 longitudinal aperture. Pharynx subspherical, 0.068 to 0.076 long by 

 0.066 to 0.082 wide; esophagus represented by a spherical ventral di- 

 verticulum ; intestinal diverticulum nearer oral sucker ; ceca wide, extend- 

 ing to near posterior end of body but not posterior to uterus. Genital pore 

 median, opposite esophagus. Testes rounded, diagonal, just anterior to 

 middle of hindbody, separated by and largely covered by uterus. Seminal 

 vesicle tubular, sharply bent once, not quite reaching acetabulum. Pro- 

 static gland compact, subspherical, about same length as sinus sac. Short 

 prostatic vesicle just outside sinus sac. Sinus sac more or less cylindrical, 

 inconspicuous, opposite intestinal bifurcation. Ovary just posterior to 

 middle of hindbody, ovoid, transversely extended. Seminal receptacle 

 large, subspherical, partly anterior and partly dorsal to ovary. Three com- 

 pact vitellaria as in other species of the genus; posterior vitellarium un- 

 lobed. Uterus voluminous with saclike coils too wide and irregular to be 

 traced, covering most organs and reaching to tips of ceca or beyond. Eggs 



