8 Franklin D. Barker and George IV. Covey 



and less flattened and continuously narrower until the posterior 

 end is reached. 



Very small spinelets are present deeply buried in the cuticula. 

 The cuticula is raised about the base of each spinelet into a 

 papilla-like structure, from the tip of which the spinelet projects. 

 These papillae are arranged in regular order, in concentric circles 

 about the oral sucker and in rows which check in all directions. 

 They are very distinct at the anterior end, but toward the posterior 

 end they become less and less distinct so that posterior to the 

 middle of the body they can scarcely be discerned (Plate I, fig. 8). 



The ventral sucker (Plate I, fig. 8) as previously stated is 

 situated at the junction of the first and second fourths of the 

 body or 0.640 mm from the anterior end, and in the mid-ventrai 

 line. It is somewhat smaller than the oral sucker. The maxi- 

 mum length and width is 0.106 mm, the minimum length is 0.059 

 mm and the minimum width is 0.079 mm. The mode for the 

 length is 0.088 mm for 23 per cent, and the mode for the width, 

 0.106 mm for 23 per cent. From these dimensions it is seen that 

 the shape of the ventral sucker varies in the different individuals, 

 the variation depending largely, I believe, on the degree of con- 

 traction or relaxation of the animal when killed, as I have seen 

 not only the ventral sucker, but also the oral sucker, and to a cer- 

 tain extent the internal organs change shape with the movements 

 of the live animal. In eight of the fourteen examined, however, 

 including the live specimen, the ventral sucker is circular in shape, 

 the variations occurring in the other six. The variation in the 

 sucker is always the same, i. e., it becomes elliptical with its long 

 axis in the transverse plane of the body of the worm (Plate I, 

 figs. I and 8). 



The subterminal oral sucker is slightly larger than the 

 acetabulum and varies also in shape in the difTerent individuals, 

 being circular in only six out of the fourteen. The maximum 

 measurements are: length 0.106 mm, width 0.145 mm; the 

 minimum measurements are : length 0.059 mm, width 0.077 mm. 

 The mode for the length is 0.106 mm for 38.4 per cent, and the 

 mode for the width 0.106 mm for 30.9 per cent. 



Posterior to the oral sucker and between it and the pharynx i< 



200 



