Helminth Fauna of the Dry Tortugas. 71 



Ground-color pink; body characteristically canoe-shape; intestine 

 with black pigment, rami with numerous short branches. Length from 

 2-5 to 3.5 mm. A small specimen, flattened, had the following dimen- 

 sions: Length 2.60; breadth, anterior 0.40, middle 0.80, posterior 0.70; 

 oral sucker 0.20; oral aperture 0.07; ova, exclusive of filaments, 0.037 

 by 0.017; length of filament 0.30. 



Host, Scarus croicensis: 



1908, July 13, 2 fish, I trematode. 



Much smaller than specimens from Pomacanthus and in poor con- 

 dition; recorded here on account of its general appearance, character 

 of the intestines, uterus and ova. 



Himasomum candidulum gen. et sp. nov. (Figs. 184-197a.) 

 Etymology: t/j.fh, strap; Toj;j.a, body. 



Body slender, nearl}^ linear, thin, the edges usually folded under 

 ventrally, especially towards the posterior end; color white. Head vari- 

 able, a muscular collar or ridge separating it from the body; oral sucker 

 nearly terminal. The muscular collar on the neck is sometimes contracted 

 until it is simpl}' a more or less prominent ridge ; at other times it may be 

 very prominent, with a thin, frill-like edge, which may be reflected (figs. 

 184a, 185-187). The musculature is less developed on the ventral sur- 

 face back of the mouth, so that there is often the appearance of a deep 

 notch, or even the entire absence of a collar. There is no pharynx; the 

 esophagus is relatively long and quite slender. The rami of the intestine 

 extend to the posterior end, where they pass mediad of the testes. Their 

 posterior ends do not unite. In some cases the intestines appear to be 

 slightly branched, especially near the anterior end, where the outlines 

 seem to show that there were very short digitations on the intestinal 

 walls. The walls may be quite irregular, but neither the mounted speci- 

 mens nor the sectioned material shows a condition which will justify 

 the statement that the intestinal rami are branched. Genital aperture 

 on the left margin at about the anterior fifth. Cirrus rather long and 

 smooth. The cirrus-pouch passes diagonally to the middle line, its dorsal 

 half lying along the middle line and inclosing the prostate gland. The 

 seminal vesicle is a slender, coiled duct posterior to the cirrus-pouch. 

 Testes 2, lobed, lateral, opposite, at posterior end of the body, their 

 anterior borders behind the level of the ovary. They are separated from 

 each other by the excretory vessel and by the intestines. The ovary is 

 lobed, nearly median, or a little to the right of the median line and a 

 short distance in front of the testes. The shell-gland is posterior to the 

 ovary, median and between the anterior portions of the testes. The 

 vitellaria consist of a number of solid masses of irregular shape, but in 

 general more or less rounded, beginning posteriorly at the anterior 

 border of the testes and extending along each lateral margin to a point 

 which is about as much in front of the ovary as that organ is in front of 

 the posterior end of the body. The folds of the uterus begin behind the 

 ovary at the shell-gland. Passing to the left of the ovary they occupy 

 the median region of the bod}^ forward as far as the base of the cirrus- 



