TREMATODES OF AUSTRALIAN BIRDS. 



199 



end the worm gradually tapers to a blunt point. There is 

 a narrow neck just behind the head-collar. The latter, 

 0*407 mm. broad, is only half as wide as the body. The 

 collar-spines are arranged in an uninterrupted, single row, 

 those along the lateral borders being the largest. There 

 are twenty-three of these spines, and special groups on 

 the ventral angles are wanting. The spines on the lateral 

 border measure 0*075 x 0*016 mm. 



The integument is 

 closely beset with 

 sharp-pointed spines 

 as far back as the ven- 

 tral sucker, where 

 they begin to diminish 

 in numbers and quite 

 disappear at a point 

 a little behind the 

 sucker. 



The oral sucker is 

 nearly spherical, 

 0*155 x 0*145 mm., 

 the ventral sucker is 

 also approximately spherical and measures 0*582 X 0*543, 

 so that the ratio of the former to the latter is about 2 : 7. 



There is a short prepharynx followed by a pharynx 

 0*133 mm. long by 0*107 mm., transverse diameter. The 

 oesophagus is 0*388 mm. long, and the bifurcation of the 

 intestine is situated just in front of the genital pore, and 

 close to the anterior border of the ventral sucker. 



The genital pore lies in the middle line close to the 

 anterior border of the ventral sucker. The testes are 

 placed one behind the other in the middle line in the middle 

 of the body, and in one specimen are approximately 

 spherical (0*582 x 0*542 mm.), in the other elliptical (0*776 



Fig. 7. Head collar and spines of Acan 

 thoparyphium spinulosum. 



