6o OSBORN. [Vol. II. 



much after the fashion of the relation of a snail's body to its 

 foot. These divisions are maintained internally to a consider- 

 able extent, as will be seen later, the alimentary and excretory 

 systems being confined to the body, or " neck," as the dorsal 

 tubular portion is called, while the reproductive system is 

 largely located in the ventral and expanded " foot." The 

 entire length of the animal from the tip of the foot behind 

 to the tip of the neck in front (in an alcoholic specimen) was, 

 in one case, 1.6 mm. ; Monticelli gives 1.7 mm. for P. lenoiri. 

 The foot, or ventral sucker, is 1.3 mm. long and i mm. broad, 

 and is thus the most prominent external feature of the animal. 



There is no differenti- 

 Tf^^f^^v-^^^ ated oral sucker, the wall 



of the body at the ante- 

 rior end being thin and 



Fig. 3. — Side view of P. a««7(/o«i'a^, showing the delicate and Strikinp"lv 



" neck '' rising from the broad foot. *-' •' 



(see Fig. 4) unlike the 

 much thickened condition found in Distomids, and generally 

 in the trematodes, where a distinct oral sucker is present. 

 The generative opening (Fig. i, G. P.) is located in the 

 middle ventral line, near the junction of the anterior region 

 with the foot. The hinder broadened portion of the animal 

 consists of a dorsal portion which shades down impercep- 

 tibly laterally and posteriorly from the tubular anterior portion 

 and fades out posteriorly to form the broad, fiat dorsal sur- 

 face of the sucker. This latter extends into an extremely thin 

 rim all around the edge of the foot, and includes a flap which 

 extends in front of the junction of the sucker with the anterior 

 region of the body. On the hinder dorsal surface of the body, 

 near the extreme posterior end, is located the opening of the 

 excretory system (Fig. i, Ex. P.). 



The ventral sucker itself is subdivided, the plan of its sub- 

 divisions being entirely unlike that of Aspidogaster, and as dis- 

 tinctly similar to that of Platyaspis. The surface of the sucker 

 (see Fig. 2) is regularly subdivided by transverse and longi- 

 tudinal folds into compartments, of which there is a distinct 

 peripheral series of 20 compartments and a median series of 

 9, making 29 compartments in all. The precise position of the 



