CONTRIBUTIONS TO AMERICAN HELMINTHOLOGY. 55 



of tke moutli of the American Bittern (Botaurus minor, Gm.) at the 

 sides of and below tlie tongue. 



The following species, according to V. Linstow's excellent " Com- 

 pendium," have been found in the cavity of the mouth or in the 

 oesophagus of Oiconise : 



1. D. complantaum cesopli Ardea cinerea. 



2. D. heterostomum sub lingua A. purpurea. 



3. B. Mans cesoph Cic. alba. 



4. D. dimorphum ... . . " A. cocoi. 



These forms are closely related; indeed, Dujardin'^ regards the first 

 two as identical with the third, and Diesing^ seems to suggest that 

 the first and fourth are also related. The separation by Diesing of 

 D. hians from these congeners, on account of the relative size of the 

 suckers, may possibly be grounded on a mistake. The anterior end 

 of the worm which I possess resembles closely that of D. dimorphum 

 (see Diesing's figure),^ and it is more than probable that the promi- 

 nent border which surrounds the mouth in these forms has been 

 taken for the anterior sucker. This it seems to replace functionally 

 in part in my specimens; for during life it undergoes rapid changes in 

 shape, sometimes having a circular sometimes a triangular aperture, 

 and plays an active part in the locomotion of the animal; while the 

 anterior sucker is quite distinct, although small, and is immersed in 

 the papilla which springs from the anterior depression. (See Fig. 1). 



The following points in the description of D. heterostomum induce 

 me to refer my specimens to it until a comparison can be made : 

 the habitat, size, two lateral lines, form of anterior end of body, of 

 neck and of ventral sucker, position of genital organs and apertures. 



The details which follow are for the most part taken from dead 

 specimens. 



The form of the body is subject to much variation. Fig. 1 repre- 

 sents it at rest. Length, 6.85 mm.; greatest breadth, 1.5 mm. It 

 may, however, lengthen into a much more linear form. The anterior 

 sucker is 0.3 mm. in diameter, its aperture transversely elliptical. 

 The pharynx has thin walls, is still smaller, and gives ofi" the intes- 

 tinal coeca immediately, which are very conspicuous from the deep 

 brown pigment in their walls. They have the further peculiarity of 



1 Helminthes, p. 399. sgystem. Helm. I. 354. 



8 Neunzehn Arten Tremat. X. B. Deakaclir. d. k. Akad. in Wien., Taf. III., 2 & 3. 



