r 
520 PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 
Rhinobatus planiceps. 
Garman, 1880, Bull. Mus. Comp. Zool. No. 11, 168. 
Disk, including ventrals, rhombic, about one and a half times as long 
as wide.’ Anterior borders of pectorals straight, more than twice as 
long as the convex posterior margins. Angles of pectorals rounded, 
the hinder not extending farther than to the vent. Outer angle of 
ventrals rounded, posterior acute. Head broad, flat. Rostral cartilage 
medium, dilated at the extremity, with the ridges close together in the 
anterior third of their length. Snout rather broad, with rounded ex- 
tremity. Eyes moderate. Spiracle immediately behind the eye, smaller 
than the orbit, with a single fold on the posterior side. Anterior nasal 
valve not dilated, posterior two-lobed. Mouth nearly straight. Body 
covered with shagreen above and below. Tail appearing as if continued 
on the posterior portion of the abdomen, much depressed, with a fold on 
each side, bearing two elevated dorsals behind the ventrals and a cau- 
dal with convex border at its extremity. Second dorsal distant from 
the caudal the length of its base. Bases of the dorsals distant from 
each other the length of the anterior borders. Scales larger over the 
central portions of the disk. Compressed hooked spines in a median 
row on back and tail, in two patches on each shoulder, and a series 
above each eye. On the young these spines are much more prominent 
and regular in size than in the adult. Color brown; light between and 
on each side of the rostral ridges; white below. Young specimens 
with a number of small, round, white spots on each side of the dorsum. 
The following measurements are taken from a young male: 
e Inches. 
Po talwlen' othe Wy ses Sat ees Seis. ce tee ose ec sie ears Oe eee cee mee te Sods eee ta ee ee ee 19.0 
Snoutiioend oblventralsys- C2 Os2o). See ee Eee RRS Re Be Ree eee 10.2 
Snoutdomontli: =.-2 649 feos Yee eee ee ee Sate Lee a eee 355) 
Width of, pectorals 44. eels Ske tte as Boe sh aeea cee neon eee ae 6.9 
Payta, Callao, and Galapagos Islands. 
SYRRHINA. 
Characters in general those of Rhinobatus. Disk somewhat shorter 
and broader. Nasal valves dilated and extending upon the internarial 
space. 
Syrrhina brevirostris. 
Miiller & Henle, 1841, Syst. Beschr. Plagiost. 114. 
Disk, including the ventrals, rhombic, longer than wide ; width about 
seven-eighths of the length. Anterior margins nearly straight, slightly 
indented opposite the gill-openings, at the end of the snout forming an 
angle of less than ninety degrees. Angles and posterior margins of 
pectorals rounded. Ventrals rounded. Posterior angle rather blunt. 
Head moderate; crown concave. Snout short, slightly rounded at the 
tip; length about twice the width of the head between the eyes. Ros- 
tral ridges distant at the head, meeting at the end of the rostrum. Eye 
