6 ON NEW GENERA AND SPECIES OF FISHES 
DASYATIDA. 
DASYATIS FLUVIORUM sp. nov. 
Disk subcircular, its length § of its width. Anterior 
borders of disk linear, meeting one another at a widely 
obtuse angle; posterior borders rather feebly, inner 
moderately convex ; outer angles broadly, posterior some- 
what narrowly rounded. Outer border of ventral fin nearly 
straight, as long as the snout ; hinder border feebly convex, 
meeting the outer at rather less than a right angle, the 
point rounded ; inner angle rounded. Width of mouth 
subequal to the space between the anterior angles of the 
nostrils. Snout shghtly projecting beyond the anterior 
contour. Free border of nasal flap minutely fringed. Lower 
lip corrugated. Diameter of eye 2§ in the width of the inter- 
orbital region, which is rather more than that of the mouth 
and 4 of the length of the disk. Jaws undulated, the 
upper biemarginate, the intervening ridge fitting into 
the mesial emargination of the lower jaw, which is strongly 
bent backwards laterally, so that its entire posterior border 
is emarginate. Upper jaw succeeded by a wide, fimbriated, 
membranous flap, bearing on its free border 30 cilia. Floor 
of mouth with 7 papille arranged in three groups; on 
each side a pair, of which the inner is the longer, the outer 
sometimes absent or vestigial, and three in the middle, 
these being more conspicuous and truncated. No rostral 
groove ; frontal region with a wide shallow tongue-shaped 
median depression, which is separated by a narrow bridge 
from a much smaller circular occipital depression. A row 
of small, open, mucigerous papille, mostly associated in 
pairs or threes, between the tip of the snout and the frontal 
depression, immediately in advance of which they form 
a small cluster ; each preorbital region with a much larger 
group of similar papille, which extends backwards above 
and below the eye and is united to the rostral system by 
an oblique series of single pores ; a small, irregular cluster 
outside of and partly anterior to the preorbital group ; 
a semicircular series on either side of and a pair, placed 
transversely, within the occipital depression; a crescentic 
biserial band of subcutaneous tubular pores below and well 
outside the eye; a similarly situated oval cluster below 
