1 



598 W. S. NICKERSON, 



The specimens of Cotylogaster occidentalis which I have collected 

 Vary in length between 8 and 10 V2 mm. The body (Fig. 1) may be 

 described as consisting of two parts: 1) an anterior, muscuhir pro- 

 boscis-like portion forming about one third of the entire length and 

 2) the body proper comprising the remaining two thirds which is 

 broader, somewhat flattened dorsoventrally and raodified on its ventral 

 surface to form the large Compound adhesive disk or sucker. The 

 first portion is capable of being retracted telescopically for one half 

 its length into the hiuder portion and is expanded at the end into a 

 five-lobed disk having the raouth at its centre. The dorsal median 

 lobe is larger than either of the others and has a pit at its apex 

 from the base of which a papilla rises (Fig. 6). This is probably the 

 seat of a sense organ of some kind and corresponds with the similar 

 structure in C. michaelis described by Monticelli. The other four 

 lobes are rounded and of nearly equal size. The incision between 

 the two ventral lobes is a little more pronounced than that between 

 any other two. The portion just back of the buccal disk, which may 

 be called the neck, is broader transversely than thick and nearly tri- 

 angulär in Gross section (Fig. 8). Its ventral side is nearly flat while 

 the middorsal line is elevated into a ridge rounded on top and 

 slightly concave on the slopes between this ridge and the somewhat 

 thickened lateral raargins. Toward its connection with the main por- 

 tion of the body the form of the neck beconies more nearly 

 cylindrical. 



The body proper is nearly elliptical in cross section, the trans- 

 verse diameter being about IV2 mm and the dorsoventral 1 mm. Its 

 posterior end is curled strongiy upward in the natural condition of 

 the living worm in all of the specimens. A broad conical elevation, 

 the dorsal cone, rises from the dorsal side near the posterior end; 

 its summit might readily be mistaken for the posterior tip of the 

 body but the i)resence of the excretory pore posterior to it and also 

 the arrangement of muscles and other internal organs show that it is 

 not such morphologically. 



The large ventral shield or sucker Covers the whole ventral side 

 of the body and extends up laterally until its edges are nearly as 

 high as the dorsal surface (Figs. 1, 9 and 10). It is a muscular 

 organ coutaining depressions or acetabula varying in number from 

 about 132 to 144. The whole median portion of the organ is oc- 

 cupied by 31—34 greatly elongated transverse grooves separated by 

 feebly developed transverse partitions or ridges and nearly equaling 



