28 DESCRIPTIONS OF FOUR DISTOMES. 



to the middle of the body. Excretory vesicle very long and voluminous, Y-shaped, 

 with a long median portion and long crura. Testes two, side by side, in the middle 

 of the body, behind the acetabulum and the ovary. Ovary immediately behind 

 the acetabulum; yolk-glands lateral, occupying the middle third of the body. 

 Cirrus-sac large, lying diagonally across the body from the acetabulum to the geni- 

 tal pore at the left edge of the body. Egg measure 0.03 millimetre by 0.019 milli- 

 metre. Parasitic in the mouth of Heterodon platyrhinus. 



This worm shows a remarkable resemblance to R. zschokkei Volz ('99), a worm 

 found in the lung of a specimen of Heterodon platyrhinus which died in a private 

 terrarium in St. Gall, Switzerland. In size the two forms are alike. They are also 

 almost identical as to their anatomy, but the Swiss form differs from the American 

 in the following particulars: it is found in the lung instead of the mouth of the snake; 

 it is without an oesophagus; the genital pore is at the right side of the body instead 

 of the left; and the folds of the uterus in the hinder part of the body have a lateral 

 direction, which is not the case in the American form. 



III. RENIFER ELONGATUS sp. nov. 



This worm (PI. IV, Fig. 2) was found in the mouth of Heterodon platyrhinus 

 together with the one just described. It is a smaller worm than R. ellipticus, and is 

 relatively more slender; the suckers are relatively longer, the intestinal caeca are 

 also longer, the yolk-glands are less voluminous, and the genital pore is near the 

 median line instead of being near the edge of the body; in other respects, however, 

 the worm is very similar to its neighbor. The length of Renifer elongatus is about 

 3 millimetres; the greatest breadth is at the beginning of the second third of the 

 body, where the large acetabulum is situated, and is 0.68 millimetre. From this 

 place the body tapers slightly towards the anterior end, to which the large oral sucker 

 gives a rounded form. Towards the posterior end the body tapers to a blunt point. 

 The body has a thickness in the region of the acetabulum of 0.4 millimetre. As is 

 the case with R. ellipticus, the worm is flat on the ventral side and cylindrical on the 

 dorsal. The entire body is thickly covered with minute spines arranged in trans- 

 verse rows, except towards the hinder end where the spines become less numerous 

 and regular. The suckers are of large size and are sessile. The oral sucker is sub- 

 terminal and has a length of 0.32 millimetre and a width of 0.33 millimetre. The 

 opening is noticeably small, having a width of 0.06 millimetre. The acetabulum 



