Fishes of the Western Nortfi Atlantic 7 5 



(Fig. 18C) though widely separated one from the other in the median line; posterior 

 margin of nostril also expanded as a blunt lobe. Dermal armature much as in Rhinobatos, 

 except that minute dermal denticles are thickly interstrewn with larger conical ones 

 on upper surface; a few on lower surface also. Generic characters otherwise as in 

 Rhinobatos. 



Size. Maximum length about three feet. 



Habits. Similar to those of Rhinobatos, so far as is known. 



Range. Known only from Brazil and along the Pacific Coast of America from south- 

 ern California and the Gulf of California southward to Panama. 



Species. Only two, the one Atlantic, the other Pacific. 



Key to Species 



I a. Dorsal fins with posterior margins longer than their bases; rostral ridges con- 

 verging anteriorly; small denticles on dorsal surface posterior to nuchal region 

 rising gently rearward or even nearly horizontal, their bases irregularly scalloped, 

 not regularly stellate or striate (Fig. 19B). 



brevirostris Miiller and Henle 1841, p. 75. 



lb. Dorsal fins with posterior margins shorter than their bases; rostral ridges nearly 



parallel; small scales on dorsal surface conical, erect, their bases conspicuously 



striate or stellate (Fig. 17). exasperata Jordan and Gilbert 1880. 



Pacific Coast of America, southern California 

 to Panama. 



Zapteryx brevirostris (Miiller and Henle) 1841 



Short-nosed Guitarfish 



Figures 18, 19 



Study Material. Four females, 445 to 480 mm long, and a juvenile male, 345 mm, 

 from Brazil, in Harvard Museum of Comparative Zoology. 



Distinctive Characters. The heart-shaped disc of Zapteryx, combined with its stout 

 muscular tail bearing two large dorsal fins, marks it off from all other batoids known 

 from the western Atlantic except for the three local Guitarfishes, Rhinobatos horkelii, R. 

 lentiginosus and R. percellens. It is separable from these by its much more obtuse snout 

 and relatively broader disc, together with the fact that the flap-like expansions of the 

 anterior margins of its nostrils almost wholly roof over the inner half of the nasal 

 apertures. 



Description. Proportional dimensions in per cent of total length. Male, 345 mm, 

 and female, 460 mm (Harv. Mus. Comp. Zool., No. 536) from Rio de Janeiro, Brazil. 

 Disc: extreme breadth 47.3, 48.7; length 42.2, 41.7. 

 Snout length: in front of orbits 9.0, 9.4; in front of mouth 1 1.9, 12.0. 

 Orbits: horizontal diameter 4.4, 3.7; distance between 4.8, 4.1. 



