8 Dr. A. Giintlier on the 



compressed into a crest behind the spine ; rather large conical 

 thorns in front of the spine, arranged partly uniserially, partly 

 biserially. Six appendages at the bottom of the mouth 

 behind the teeth. 



An adult male, with the disk 10 inches long and broad, 

 from the Parana, has the upper part of the disk ornamented 

 with white ocelli, and nearly the whole of the lower parts of a 

 brown colour. 



5. Trygon hrachyurus, sp. n. 



This species differs from Trygon hystrix in several impor- 

 tant points. The eye is small, its longitudinal diameter being 

 two fifths of the width of the cartilaginous space between the 

 eyes. Spiracles of moderate width, about twice the size of 

 the orbit. Tail much shorter than the body, with a low fin 

 behind the dorsal spine and a very low fold of the skin along 

 its lower side : the thorns in the median line of the tail in 

 front of the spine are very small, arranged in a single series. 

 Five appendages at the bottom of the mouth behind the teeth. 

 Upper parts greyish brown, with a coarse network of blackish 

 streaks; lower parts white, with the margins of the disk 

 blackish. 



A female from Buenos Ayres shows the following dimen- 

 sions : — length of the disk 10 inches, width of the disk 12 

 inches ; length of the tail 9 inches. 



5 a. Trygon reticulatus } sp. n. 



Eye of moderate size, half the width of the cartilagi- 

 nous space between the eyes. Spiracles scarcely twice the 

 width of the orbit. Tail considerably longer than the disk, 

 with a very low fold above and a still lower one below its 

 terminal half; median line of the tail with a series of thorns 

 of moderate size, irregularly arranged. Four appendages at 

 the bottom of the mouth behind the teeth ; upper part brown, 

 with a network of black lines, the meshes being hexagonal 

 and wide ; lower parts uniform white. 



A male from Surinam has a disk 7^ inches long and 8^ 

 inches broad; the tail is 12 inches. 



This is the species which I have described in the ' Cata- 

 logue of Fish ' as Trygon hystrix of Muller & Henle. 



6. Myliobatis aquila, L. 



ACANTHOPTERYGIANS. 



7. Otolithus guatucupa, C. & V. [Ch.~\ 



8. Ancylod&n atricauda } Gthr. [Ch.] 



