542 W. G. MacCällum, 



tracted condition. The anterior extremity is coiiverted into a spread- 

 ing- somewliat reniform structure whicli is flat ventrally and in the 

 Center of whicli on the fiat side there is a small sucker which is 

 perforated and constitutes the month. This expanded disc measures 

 1.4 mm transversely and .8 mm to 1.04 mm antero-posteriorly while 

 the mouth sucker measures only .2 mm the actual orifice being- 

 .16 mm in diameter. The margin of the disc is set with a Single 

 row of chitinous spicules 47 in number as seen in the drawing. 

 Those at the posterior angles of the disc are slightly inclined 

 to double up as regards the line of insertion but in general they 

 maintain one straight line. The spicules are straight and coni- 

 cal but although they present but one form they are not all of 

 the same size — the largest lateral ones measure .08 X -O-^ im^i 

 while anteriorly there are four or five which are smaller measuring 

 .03 X -015 mm. Otherwise the skin surface is entirely smooth and 

 unarmed. 



As shown in the drawing there is a depression behind the head 

 disc bounded at the sides by folds which run backward from its 

 posterior angles and between which quite close to the anterior 

 extremity lies the large ventral sucker. In the hardened worm this 

 is quite deeply sunken between the neck-folds but doubtless the 

 living- worm can protrude it to a certain extent. It is very mucli 

 larger than the mouth sucker and its cavity extends in a backward 

 direction. The orifice whicli is practically round measures .5 — .8 mm 

 in diameter while the outer diameter of the sucker is 1.25—1.38 mm 

 and its depth is 1.2 mm. 



In the i'eceding space between the acetabulum aiul the- reniform 

 head disc there opens the genital cloaca, the orifice being situated 

 just anterior to the acetabulum in the median line. 



The greater portiou of the body lies behind the acetabulum 

 which reaches only 2 mm fi'om the anterior extremity. In the median 

 line dorsally quite far back there may be found the niinute orifice 

 of Lauker's canal while at a point just in front of the posterior end 

 of the body and also dorsally there is the orifice of the excretory 

 System. 



The worm is greyish-white in color, in the hardened section 

 at least, and the vitellarium shows through as a blackish margiii 

 which extends from the region of the acetabulum alniost to the 

 posterior end although it is not continuous with that of the opposite 

 side at the posterior extremity. In tlie median line behind tlie 



