704 MacCALLUM. [Vol. XV. 



closely related to D. heterostomiim. These were collected in 

 various places, and from several different hosts. They are : 



Clinostovunn gi'acile Leidy. 

 Distomum galactosomum Leidy. 



In addition to these, I have the specimens described by R. R. 

 Wright, under the name Distomum gracile, from the branchi- 

 ostegal membranes and fins of Perca flavesccns. Another 

 specimen, which I labeled D. gracile, I found encysted in the 

 pectoral muscles of a frog in 1895. Other specimens found 

 encysted in a trout have been determined by Stiles and Hassall 

 as Clinostomum heterostomum. Finally, I have a number of 

 specimens of an immature distome found encysted under the 

 skin of Ictahirus dngesi, collected in Mexico. These, also, I 

 have received from Dr. Hassall. All of these are immature 

 forms. 



In his original description of Clinostomum gracile (10), Leidy 

 describes the prominent margin about the mouth-sucker, which 

 is smaller than the acetabulum. The length is 3 lines, breadth 

 I line. Habitat — intestine of Esox, and encysted in gills, fins, 

 and muscles of Pomotis vulgaris and Microfteriis dolomieu. 



R. R. Wright (6) later identifies this form with the D. gracile 

 of Diesing (12), which he describes from the perch. He gives 

 a detailed description of the large acetabulum with its trian- 

 gular aperture, but saw no trace of genital organs, and suggests 

 that the sexually mature form might be found in some larger 

 fish or piscivorous bird. Attention is called to the large pig- 

 mented intestinal coeca, and more particularly to the subcu- 

 ticular meshwork of the watervascular system communicating 

 with a wide median stem. Diesing's own description is not 

 at all detailed. 



Leidy's description of D. galactosommn (11) is briefly as fol- 

 lows: Habitat — Roccns lineatus. Anterior sucker surrounded 

 by a prominent margin — body unarmed — ventral sucker sessile 

 with triangular aperture; larger than anterior. Size 6-12 mm. 

 by 2-2.5 "^ni- Intestines extend from the small pharynx to 

 the tail, tortuous, and sacculated. The animal has a reticular 

 appearance, due to a network of opaque white lines communi- 



