Fishes of the Western North Atlantic 



13 



in regarding them as sole members of one of the primary divisions, ranked here as a 

 suborder (Torpedinoidea, p. 80). The thirty-odd species concerned have been united 

 commonly in a single family, but they are distributed here among three families (for 

 further discussion, see p. 86). The presence of horny rays (ceratotrichia) as well as 

 of cartilaginous radials in their unpaired fins (a shark-like character) relates them more 

 nearly to the rhinobatoids than to any other batoids. 



The batoids that remain after the subtraction of the Electric Rays fall in four 

 fairly well definable groups of species, classed here as suborders. 



Figure 2. Pristis perotteti, juvenile male, about 1,376 mm long, from Lake Nicaragua (U. S. Nat. Mus. 

 No. 120468). 



A. The Sawfishes (Pristoidea). Snout prolonged as a narrow blade-like "saw," its 

 either edge armed with a single series of large tooth-like structures; tail sector stout; 

 two well developed dorsal fins, the first originating over or anterior to the pelvics; a 

 large caudal fin; pectoral fins attached to head only a little past the gills; outer margins 

 of pelvics straight or convex; the paired fins, as well as the unpaired, with horny rays 

 (ceratotrichia) in addition to the cartilaginous radials. 



B. The Guitarfishes (Rhinobatoidea). Snout not blade- or saw-like; tail sector 

 stout; two well developed dorsal fins, the first originating much nearer to tips of pelvics 

 than to tip of tail ; a well developed caudal fin ; pelvics with the outer margins convex, 

 or at least not notched ; their unpaired fins, like those of the Sawfishes and Torpedoes, 

 have horny rays as well as cartilaginous radials, as do the unpaired fins of the Sharks, 

 but not their paired fins. 



C. The Skates (Rajoidea). Tail more slender and without spine; one or two small 

 fins, or none; fins with cartilaginous radials only (no horny rays); the origin of first 

 dorsal (if any) much nearer to tip of tail than to tips of pelvics; caudal fin reduced to 

 a low fold finely striate in structure; the outer margins of pelvic fins more or less 

 deeply concave. This group is typified by the common Skates. 



D. The Rays (Myliobatoidea). Tail ranging from moderately to excessively slen- 

 der; one dorsal fin or none; dorsal fin, if present, well forward on the tail, anterior to 

 tips of pelvics or close behind them; pelvics with outer margins not concave; some 



