28 PROCEEDINGS OF THE NATIONAL MUSEUM vol.81 



enlarge relatively more rapidly, after reaching sexual maturity, than 

 the anterior end, since the former is essentially a sac for holding 

 the genital organs. 



Gercorchis texcunus resembles most closely Cercorchis corti de- 

 scribed by Stunkard in 1916. The differences that seem to justify 

 the erection of a new species are : The longer esophagus, more than 

 twice as long as in G. corti^ the longer metraterm, and the distribu- 

 tion of the vitellaria, which begin at a point more cephalic than in 

 G. coi'ti. 



CERCORCHIS BAIRDI, new species 



Plate 2, F^qurb 7 



Specific diagnosis. — Gercorchis: Sexually mature worms are 2.9 

 to 2.95 mm in length and 0.38 to 0.36 mm in width. The cuticular 

 spines at the anterior end are very fine, scarcely distinguishable even 

 with the aid of an oil immersion objective; the rows are less than 

 1/i apart. The oral sucker is usually wider than long, it varies from 

 Y2/X, to 96/A in length and from SSjn to 114/i in width. The acetabulum 

 is small and circular in outline. It measures 84/x in diameter. It is 

 0.46 to 0.5 mm from the anterior end. A prepharynx is lacking, and 

 the pharynx is a globe measuring 40;a to 58/j. in diameter. The 

 esophagus is of medium length, varjdng from 63)u to 84/x. The 

 intestinal ceca extend beyond the testes, and nearly to the posterior 

 end. The ovary is globular in outline and lies on either side of the 

 body. It is 80;u to lllju, in diameter and in my material is slightly 

 caudal to the first third of the body length. The shell gland and 

 ootype lie immediately behind the ovary. The ascending and de- 

 scending coils of the uterus do not cross, but frequently they overlie 

 the intestinal ceca. The metraterm is thrown into numerous waves. 

 The eggs measure 32/x, by 20/^. The vitellaria lie outside the intes- 

 tinal ceca. Their farthest anterior extent is the level of the ante- 

 rior margin of the ovary. Their farthest caudal extent is usually 

 about the diameter of the anterior testis, cephalic to that organ. 

 The testes are usually circular in outline, lying adjacent to each 

 other, and of about equal size. They measure 0.13 mm in diameter. 

 The cirrus sac is much coiled and stops well short of the ovary. It 

 extends through four-fifths of the ovarian-genital pore distance. 

 The vas deferens is not coiled. 



Host. — Sternothems carinatus. 



Habitat. — Intestine. 



Locality. — Huntsville, Tex. 



Type specimen.— U.^.'^.U. Helm. Coll. No. 30891. 



Remarks. — This form resembles Gercorchis mediits Stunkard 

 (1916) very closely. It is, however, a slightly smaller form, the 



