\o. 2322. TREMATODE FAMILY HETEROPHYIDAE— RANSOM. 559 



space between the right testis and ovary. Distance from the trans- 

 verse vitelline ducts to the center of the ventral sucker usually some- 

 what less than the distance from the latter to the anterior limits of 

 the vitellaria. Eggs yellowish-brown, 30 to 35 \t. long by 16 to 20 \i. 

 wide. 



Host. — Harbor seal (Phoca vituUna). 



Location. — Intestine. 



Locality collected. — Washington, District of Columbia (National 

 Zoological Park). 



Type specitnens. — United States National Museum Helminthologi- 

 cal Collections No. 4279, collected by Dr. Albert Hassall, December 

 21, 1905. 



C otylophallus similis is very close to G. venustus, but is distinguish- 

 able from the latter by the relatively greater development of the 

 vitellaria anteriorly and their restricted development posteriorly. 

 In C. venustus there are not only a greater number of lobules of the 

 vitellaria along the outer sides of the intestinal ceca, but the number 

 in the spaces between the right testis and ovary and behind the left 

 testis is much greater than in C. similis. Another ahnost constant 

 difference is seen in the ratios of the distances between the transverse 

 vitelline ducts, ventral sucker, and anterior limits of the vitellaria. 



Genus CENTROCESTUS Looss, 1899. 



Generic diagnosis. — Heterophyidae : Mouth surrounded by a double 

 crown of spines, Prepharynx long. Pharynx near the bifurcation 

 of the intestine. Intestinal ceca extend into the posterior region of 

 the body. Ventral sucker median. Genital sinus median, imme- 

 diately in front of the ventral sucker. Prostatic portion of vas 

 deferens well developed, situated along tlie right side of the ventral 

 sucker. Well-developed seminal vesicle behind the ventral sucker, 

 arranged in a U-shaped loop extending across the median field, the 

 anterior limb of the loop the longer, base of the U to the left. 

 Testes oval, elongated transversely, near posterior border of body, 

 side by side, right and left of the median line. Seminal receptacle 

 median, in front of testes. Ovary to the right of the seminal recep- 

 tacle, in front of right testis, ovoid in form. Vitellaria arranged in 

 numerous lobules in the lateral fields, extending from the region be- 

 hind the testes nearly to the bifurcation of the intestine, encroaching 

 upon the median field in front of the ventral sucker, and extending 

 in this region inwards to or nearly to the median line. Transverse 

 vitelline ducts in neighborhood of boundary between the ovarian and 

 testicular zones. Uterus arranged in a few transverse loops, in the 

 space between the testes and the ventral sucker. Terminal portion of 

 uterus (vagina) passes forward to the genital sinus along the left 

 side of the ventral sucker. 



Type species. — Centroeestus cuspidatus (Looss, 1896) Looss, 1899. 



