ART. 17 PAEASITES OF AMPHIBIA AND EEPTILIA — HAEWOOD 35 



should more material become available it may be necessary to com- 

 bine some of the forms that are here treated separately. 



OOCHORISTICA NATRICIS, new species 



Plate 3, Figure 2 



SpecifiG diagnosis. — Ooclioristica: A flat white worm. The total 

 length is about 13 cm. The scolex is 0.5 to 0.6 mm in diameter. The 

 suckers vary from 0.16 by 0.22 mm to 0.22 by 0.3 mm. They are, 

 therefore, very large oval structures, with their long diameters lying 

 parallel with the long axis of the worm. The neck is 0.3 to 0.35 mm 

 wide and from 1 to 2 mm long. When the segments first appear they 

 are very short. The mature proglottids appear some 30 to 40 mm 

 from the scolex. They vary considerably in shape but are usually 

 somewhat longer than wide. Extreme measurements for my material 

 are 0.75 mm long by 0.80 mm w^ide and 0.105 mm long by 0.7 mm 

 wide. The genital pore lies at the caudal border of the first fourth 

 of the proglottid or slightly posterior to that level. The cirrus sac 

 is an oval structure that measures 0.65 by 0.22 mm to 0.9 by 0.18 mm. 

 A much coiled vas deferens, which acts also as a seminal vesicle, 

 extends mesad from the inner end of the cirrus sac nearly to the 

 median line. The testes lie in the caudal portions of the proglottid, 

 but extend cephalad to or slightly beyond the caudal boundary of 

 the ovary. There are 50 to 70 testes in each segment. The vagina 

 opens into the genital atrium just caudal to the cirrus sac. As in 

 other members of the genus it remains on the caudal side of the male 

 ducts. Before reaching the median line the vagina curves caudal 

 between the halves of the ovary and ends in a small seminal re- 

 ceptacle, lying ventral to the shell gland. The bilobed ovary and 

 the vitellaria crowd the small shell gland between them. The 

 ovarian complex is an oval mass measuring 0.3 by 0.6 mm. The 

 sexual ducts pass between the main tubes of the excretory system. 

 The ripe segments are about twice as long as broad. The eggs are 

 scattered singly in capsules. They are 42ju in diameter; and their 

 embryos are 20)U in diameter. 



Host. — Natrix rh ombifera. 



Habitat. — Intestine. 



Locality. — Houston, Tex. 



Tyye s^oe^'meT?,.— U.S.N.M. Helm. Coll. No. 30897. 



Remarks. — This form most closely resembles 0. zonun Baylis, but 

 it is a slenderer form with more elongate segments. In O. sonuri 

 the scolex is 0.9 to 1 mm wide, and the maximum width is 3 mm. In 

 0. natriois the scolex is only 0.6 mm wide, and the maximum width 

 is less than 1 mm. There are structural differences in the distribu- 

 tion of the testes, size of cirrus pouch, and other minor features. 



