12 • THE VOYAGE OF H.M.S. CHALLENGEE. 



Distance from the vent to the extremity of the snout, 13^ inches; distance from 

 the vent to the extremity of the tail, 11^ inches; greatest width of the disk, 21 

 inches. 



A single adult specimen has been obtained. 25 inches in length. Station 321. 

 Kiode la Plata ; 13 fathoms. 



Raja microps, n. sp. (PI. IV., f natural size). 



A short-snouted species. The angle formed by the margins of the snout is obtuse, 

 and the extremity does not project. The width of the interorbital space is much more 

 than the length of the orbit together with the spiracle, and is contained twice and two- 

 thirds in the distance between the eye and the end of the snout. Mouth very slightly 

 curved ; teeth obtuse, in about forty series in the upper jaw. The outer pectoral angle 

 is rounded, but the margins would meet at a right angle. The two dorsal fins close 

 together, separated by a spine only. Minute roughnesses on the snout, the inter- 

 orbital space, along the median line of the back, and along the front margin of the 

 pectoral fin. A single spine in the middle of the back, and a series of spines along the 

 median line of the tail. The muciferous tubes behind the head are very conspicuous, 

 and arranged Hke a fan on each side of the occiput ; each opens by a pore. Uniform 

 brown above, white below. 



Distance of the vent from the extremity of the snout, 7\ inches ; distance of the 

 vent from the extremity of the tail, 8^ inches ; width of the disk, 11 inches. Length of 

 specimen, 15f inches. 



The single specimen examined is a young male. 



Eio de la Plata. Station 321 ; 13 fathoms. 



An adult female (disk, 23 inches wide) received lately by the British Museum, from 

 Buenos Ayres, has a single curved spine, with a broad base on each side, near the front 

 margin, on a level with the spiracles. 



Ancylodon atricauda, n. sp. 



D. ^, A. 12. The height of the body is somewhat less than the length of the 

 head, which is one-third of the total (without caudal). Eye of moderate size, equal to 

 the width of the interorbital space, and shorter than the snout. The maxillary does 

 not extend to the posterior margin of the eye. Lower jaw projecting beyond the upper, 

 the mandibular teeth being outside the upper lip. The canine teeth are comparatively 

 smaller than in Ancylodon jacididens. Vertical fins scaly. The middle caudal rays 

 prolonged into a narrow pointed lobe. Scales small, silvery, with the caudal lobe 

 black. Length of specimen, 5 inches. Mouth of the Eio de la Plata. Station 321; 13 

 fathoms 



