4 3 o Memoir Sears Foundation for Marine Research 



Size. The claspers on the largest specimen seen, 220 mm long by 103 mm broad, 

 were still small (Fig. loi). The size at maturity is not known. 



Developmental Stages. Embryos have not been seen. 



Habits. The two specimens taken so far were from a depth of 20-30 fathoms on 

 muddy bottom. 



Range. Known only from the mouth of the Amazon, Lat. 1° 06' N, Long. 47° 53'W. 



Reference : 



Urotrygon microfhthalmum Delsman, Mem. Mus. Hist. nat. Belg., (2) J Fasc. 21, 1 941 : 65, 66, fig. 8 (descr., 

 ill., mouth of Amazon). 



Urotrygon venezuelae Schultz 1949 

 Figure loi a 



Study Material. Female (type), 255 mm long, from Gulf of Venezuela (U.S.Nat. 

 Mus., No. 12 1 966). 



Distinctive Characters. This species could hardly be confused with any other 

 western Atlantic Ray, except for U. microphthalmum (p. 428) or Urolophus jamaicensis 

 (p. 420). It is separable from the first of these by its generally prickly back (smooth on 

 microphthalmum) with a median row of slightly larger spines from the nuchal region 

 rearward along disc and anterior part of tail. The readiest field mark to separate it from 

 Urolophus jamaicensis is that its tail from center of cloaca is somewhat longer than the 

 distance from center of cloaca to tip of snout (shorter in Urolophus jamaicensis), and its 

 disc is considerably wider relatively, with the tip of snout more prominent (cf. Fig. 

 loi a with 99). 



Description. Proportional dimensions in per cent of total length. Female, type, 

 255 mm long, from Gulf of Venezuela (U.S.Nat. Mus., No. 121966). 

 Disc: extreme breadth 54.2; vertical length 47.6. 

 Snout length: in front of orbits 12.8; in front of mouth 12.8. 

 Orbits: horizontal diameter 2.5; distance between 6.2. 

 Spiracles: length 3.3; distance between 7.2. 

 Mouth: breadth 5.8. 



Exposed nostrils: distance between inner ends 6.0. 

 Gill openings: lengths, ist 2.4; 3rd 2.4; 5th 1.4; distance between inner ends, 



ist 12.2; 5th 8.0. 

 Pelvics: length of anterior margin 9.8. 



Distance: from tip of snout to center of cloaca 46.2 ; from center of cloaca to or- 

 igin of tail spine 24.3; to tip of tail 53.8. 



Disc about i.i times as broad as long; space between orbits slightly concave 

 transversely; snout pointed, projecting rather noticeably; outlines concave close behind 

 tip of snout, thence broadly and uniformly convex to rear corners, the latter more 

 abruptly rounded; inner margins short and weakly convex. Axis of greatest breadth 



