A New Species of Trematode 23 



neglects to say just how far they do extend. In my specimens 

 they never extend farther forward than the ovary. 



The length of his specimen is 3.150 mm and the width 0.455 

 mm. Now, since it seems evident that his measurements are from 

 a single specimen, they may be anywhere between a minimum 

 and a maximum. Comparing this with mine, the mode for the 

 length for my species is 2.013 i^"^? y^t in four of the fourteen 

 specimens compared the length exceeds 3.000 mm, and in two of 

 the four it is greater than 3.150 mm. But in no one of these four 

 does the width exceed 0.275 "^"^> which is a little more than half 

 that of his specimen, and in only two of the other ten, which two 

 are exceedingly contracted in length, thus increasing their width, 

 does the width approach that named by Stafford, the width being 

 0.450 mm in one and 0.458 mm in the other. All other measure- 

 ments given, such as that of suckers, esophagus and pharynx, are 

 as much greater in his specimen than in mine as his specimen 

 is larger than mine, though they have the same relative size as 

 do mine. 



By reference to PI. I, figs. 2 and 8 it will be seen that my 

 species is widest near the anterior end and that the posterior end 

 is more pointed than the anterior, while T. angustum is widest 

 some distance posterior to the ovary and the anterior end is rela- 

 tively more pointed than the posterior, i. e., the borders converge 

 more rapidly toward the anterior. 



As to the excretory system he says, " The unpaired part of the 

 excretory system branches, I think, at the posterior testis." In 

 my specimens it branches just posterior to the ovary, but Stafford 

 could easily have been mistaken in this point, for only a few of all 

 those which I mounted in toto showed the unpaired portion of 

 the excretory system and it was only after making cross and 

 sagittal sections that I could be certain of its position. 



Neither in his descriptions nor in his drawing of the trematode 

 which he found in the intestine of Chrysemys picta does Stafford 

 indicate the presence of a Laurer's canal, a shell gland or a recep- 

 taculum seminis. Nor does he mention a seminal vesicle, pars 

 prostatica or prostate gland in connection with the male genitals, 



215 



