Helminth Fauna of the Dry Tortugas. 41 



The specimen was stained and mounted and found to agree closely 

 with D. pectinatum. There is a slight difference in the proportions of 

 the suckers. In this specimen the ventral sucker is rather less than 1.5 

 times the diameter of the oral, while in the Beaufort forms the ventral 

 sucker is twice or more the diameter of the oral. Dimensions in balsam: 

 Length 1.86; breadth 0.30; neck 0.67; oral sucker 0.14; pharynx, length 

 0.14, breadth 0.07; ventral sucker 0.18; ova 0.024 by 0.017 and 0.020 by 

 0.014. 



Lepocreadium truUa (Linton). (Figs. 71-74.) 



Distomum trulla, Linton, Proc. U. S. Nat. Mus., vol. xxxiii, p. 109, plate xi, 

 fig- 79- 



The distomes here considered agree closely with those found in 

 Ocyurus chrysurus in Bermuda. 



Body pyriform, truncate at posterior end, triangular in outline when 

 compressed; covered with small, low, rounded spines; oral sucker equal 

 to or slightly exceeding the ventral. The pharynx is separated from 

 the oral sucker by a very short prepharynx, and the esophagus is so 

 short that it is indistinguishable in most of the mounted specimens. The 

 intestines extend to near the posterior end. From a point opposite the 

 caudal border of the ventral sucker to the posterior end the intestinal 

 rami are thick-walled, the columnar cells staining deeply. Testes 2, 

 near posterior end, diagonally placed and near together. Genital aper- 

 ture median, ventral to bifurcation of the intestine. Cirrus-pouch long- 

 clavate, inclosing the seminal vesicle at its posterior end, which is behind 

 the ventral sucker and close to the anterior edge of the anterior testis; 

 prostate conspicuous in cirrus-pouch from seminal vesicle to near the 

 genital aperture. Ovary 3-lobed, in front of testes, contiguous to anterior 

 edge of anterior testis and a little to the right of the median line. Semi- 

 nal receptacle in front of anterior testis, to the left of the ovary, and near 

 the caudal end of the cirrus-pouch. Vitelline glands diffuse, abundant, 

 filling the posterior and lateral regions of the body as far forward as the 

 pharynx. Uterus with rather numerous ova between the anterior testis 

 and the ventral sucker; the thick-walled and glandular metraterm lies 

 on the left side of the cirrus-pouch. The excretory vessel is not clearly 

 defined in the mounted specimens, but it was seen as a relatively large, 

 inflated vessel in living specimens, most conspicuous at the posterior 

 end where the opening was surrounded by radiating lines in a definite 

 area (fig. 73). 



The spinose cuticle has a tendency to separate rather easily. Many 

 of the mounted specimens show no signs of spines and others have but 

 few. Fresh specimens in good condition are conspicuously spinose. 



In 8 out of 12 the oral sucker was larger than the ventral, in the 

 remaining 4 the suckers were equal; even where the oral sucker is the 

 larger the difference is slight. In one the oral sucker measured 0.168 

 and the ventral 0.154; in another they were 0.158 and 0.144 respectively. 



Host, Ocyurus chrysurus: 



1907, July 10, 3 fish, few distomes; July 12,3 fish, few distomes. 



