Fishes of the JVestern North Atlantic 419 



anterior sector forming a blunt angle, with or without a low papilla marking tip of snout. 

 Tail from center of cloaca not longer than body from center of cloaca to tip of snout; 

 one or two formidable tail spines, their margins armed with sharp recurved teeth; tail 

 without membranous folds above or below, apart from caudal fin. Usually no dorsal 

 fin after birth, but embryos of some species may have one.*^ Caudal fin at least ^4 as 

 broad as long, extending around tip of tail and supported by cartilaginous rays. Spir- 

 acles close behind eyes; embryos of at least some species with a well developed fleshy 

 lobe or tentacle on inner margin of spiracle, directed outward across opening of latter, 

 but this is lost either before birth or shortly thereafter. Nasal curtain with fringed 

 margin; outer (morphologically posterior) margin of nostril smoothly rounded, not 

 expanded, but inner (morphologically anterior) part with a fold projecting shelf-like 

 toward nasal septum. Mouth small, transverse, its floor usually with five to nine fleshy 

 papillae, its roof with a broad curtain-like transverse fold, deeply fringed with simple 

 lobes. Teeth small, numerous, up to 10—12 rows in function simultaneously. Upper 

 surface of disc and of tail either wholly naked apart from tail spines or roughened with 

 small spines or tubercles along midzone and on shoulders. Characters otherwise those of 

 the family. 



Developmental Stages. In the Australian Urolophus testaceous, and probably in other 

 members of the genus as well, the walls of the uteri of gravid females are clothed with 

 long filiform villi, richly supplied with blood vessels. It has been suggested that the 

 external gills of early embryos may absorb nourishment from these villi, with which 

 they become entwined.*^ 



Range. Shallow coastal waters in western tropical and subtropical Atlantic; eastern 

 North Pacific from Gulf of Panama to southern California (Point Conception) ; Japan 

 and Korea; Malay Archipelago (Ki Islands); Victoria, New South Wales, South 

 Australia, and Tasmania. 



Species. Recent surveys'^ recognize seven (perhaps eight'*) species of Urolophus, 

 as here defined, in the western Pacific-Australian region and three along the eastern 

 shores of the Pacific, besides the one (U.jamaicensis) that occurs in the Atlantic. They 

 fall in two groups: A. Those with midbelt of disc more or less roughened with tubercles 

 from soon after birth. This subdivision includes U.jamaicensis (Cuvier) 18 17 of the 

 Atlantic and U. armatus Miiller and Henle 1841 (if this is actually a species of the 

 genus Urolophus rather than of Trygonoptera with dorsal fin*^), known only from the 

 Bismarck Archipelago. B. With skin wholly naked apart from tail spines. The members 

 of this group stand in obvious need of a critical revision which we are not in a posi- 

 tion to attempt. 



91. Some embryos of Urolophus cruciatus from Australian waters have a small dorsal fin, but others in the same litter 

 may not (Whitley, Fish. Aust., i, 1940: 215, 216). 



92. See Haswell, Proc. Linn. Soc. N. S. VV., j, 1889: 1716. 



93. Beebe and Tee-Van (Zoologica N. Y., 26, 1941: 269) as Urobatis; Whitley, Fish. Aust., i, 1940: 215; Fowler, 

 Bull. U.S. nat. Mus., 100 {13), 1941: 440. 



94. Firsthand descriptions of U. armatus Miiller and Henle 1841 from New Ireland, Bismarck Group, fail to state speci- 

 fically whether it does or does not have a dorsal fin. 



95. See p. 417, footnote 85. 



27* 



