250 ^^- S- NiCKERSON, 



Cephalogonimus given by Looss (1899) and is unqiiestionably closely 

 related to tlie members of tliat genus already known. 



Cephalogonimus vesicaudus is a rather small worm tlie average 

 leiigth of preserved specimens being from IV2 to 2 mm and tlie 

 widtli 0,8—1 mm. The greatest lengtli wliich I have recorded is 

 3,5 mm and the maximum widtli 1,3 mm. The smallest specimen 

 that I have measured was 1^4 mm in length. The posterior end is 

 broader and rounded, the anterior somewhat tapering giving an 

 ovoidal outline as in Fig. 6. Preserved specimens nearly always 

 have a strong ventral curvature due to contraction of the longitu- 

 dinal muscle-fibers which are developed more strongly than elsewhere 

 in two lateral bands upon the ventral side of the body. The 

 acetabulum is a little larger than the oral sucker and is situated 

 about % of the length of the animal from its anterior end. The 

 diameters of the two suckers are respectively about 0,27 and 0,22 mm. 

 My maximum and minimum measures recorded are for the acetabulum 

 314 and 222 f^ for the oral sucker 260 and 204 //. These measure- 

 ments were made upon preserved specimens. 



The whole ventral surface is thickly set with scales arranged 

 in the usual oblique rows. In the mid-ventral region they are broad 

 and flat with the lateral edges parallel and abruptly rounded ends 

 giving an outline which may be compared to that of the blade of 

 a round pointed shovel. The larger ones measure 14 — 16 fi in 

 length by 10—12 n in breadth. Toward the ends of the body and 

 the lateral margins they become narrower and more claw shaped. 

 Upon the dorsal surface the spines are absent except upon the most 

 anterior part; they are here very small and become progressively 

 more minute backward until they entirely disappear not farther 

 back than over the pharynx. Fischee (1884) describes OpistJwtrema 

 as having spines on the ventral but lacking them ou the dorsal 

 surface, but so far as I know this peculiarity of distribution of 

 spines is not common in trematodes. 



The condition of the digestive System agrees with that of the 

 two other species except in the absence of an esophagus. The 

 Pharynx which measures about 60 ß in length by 100 /^ in trans- 

 verse diameter follows immediately upon the oral sucker and 

 frequently shows a four-lobed condition at" its anterior end. The 

 intestinal coeca begin immediately back of the pharynx, there being 

 no intervening esophagus, and terminate a little less than oue fourth 

 of the worm's length from its posterior end. The other two species 



