432 Memoir Sears Foundation for Marine Research 



One tail spine, its origin posterior to center of cloaca by a distance about as great 

 as distance from tip of snout to level of fourth pair of gill openings; its length nearly 

 as great as length of snout in front of eyes. 



Back naked along posterior margins of pectorals but roughened elsewhere on disc 

 and tail with small prickles, those anterior to eyes sharp-pointed and set so close together 

 that bases are in contact; those elsewhere on disc more loosely spaced and mostly blunt- 

 tipped or rounded; mid-dorsal line from nuchal region to tail spine with an irregular 

 row of about 45 blunt spines a little larger than the prickles elsewhere on disc and tail; 

 mid-dorsal spines on tail slightly larger than those on disc; sides of tail prickly to tip; 

 upper caudal lobe prickly, but lower lobe smooth; pelvics and skin over eyes smooth. 

 Lower surface smooth. 



Snout in front of eyes about 2.1 times as long as distance between inner margins 

 of orbits and about 5.1 times as long as eye. Eye about 40 "/o as long as distance between 

 orbits. Spiracles close behind orbits and about 1.3 times as long. First gill openings 

 about Vs as long as breadth of mouth; fifth gill openings about 60 7o as long as first; 

 distance between inner ends of first gill openings about as long as snout in front of 

 eyes and about twice as long as breadth of mouth; distance between inner ends of fifth 

 gill openings about V3 as long as distance between first gills. 



Teeth f*, ovoid, without definite cusp, close-set in quincunx. 

 Caudal fin about Yeas broad as long, with rounded tip; origins of upper and lower 

 sides opposite. Pelvics with nearly straight anterior margin, weakly convex distal mar- 

 gin, and rather abruptly rounded corners; anterior margin about V? as long as distance 

 from origin to rear corner, the latter reaching rearward from level of rear limits of 

 pectorals for a distance about half the length of snout in front of eyes or about Va of 

 distance from level of rear corners of pectorals toward origin of tail spine. 



Color. Plain greyish brown above, without markings but seemingly faded (in 

 alcohol); cream-colored below. 



Size. The length of the only specimen seen (255 mm) gives no clue as to the size 

 this species may reach at maturity. 



Relationship to Extralimital Species. This Ray, as remarked by its discoverer,"^ 

 appears to be the Atlantic representative of U. asterias (Jordan and Gilbert) 1883 of 

 the Pacific coasts of Mexico and Panama, which, alone among eastern Pacific represen- 

 tatives of the genus, has a generally prickly back with a continuous row of somewhat 

 larger spines along the mid-dorsal line."* But U.venezuelae differs from U. asterias in 

 that its mid-dorsal spines are only a little larger than the prickles elsewhere on the back 

 (much larger and more prominent in asterias), and that its eye is smaller relative to the 

 length of the snout.^" 



113. Schultz, Proc. U. S. nat. Mus., gg, 1949: 26. 



114. See Beebe and Tee- Van (Zoologica N. Y., 26, 1941: 264-268) for a recent survey of eastern Pacific species of 

 Urotrygon. 



:i5. Snout, anterior to eyes, about five times as long as eye in U. 'venezuelae, not more than four times on the type 

 specimen of U. asterias (Schultz, Proc. U.S. nat. Mus., gg, 1949: 26, table I). 



