RHACHINOTUS. 



373 



Rusty brown above; whitish below. Secured by the Hassler Expedition 

 at Mejillones, Chile. 



Dasybatidae. 



Body head and pectorals depressed, together forming a broad disk, in which 

 the pectorals meet in front of the cranium forming the snout without a supporting 

 rostral cartilage. Spiracles large close behind the eyes. Anterior nasal valves 

 confluent across a narrow isthmus, reaching the mouth. Mouth transverse, 

 more or less curved. Teeth small, in quincunx, tessellated. Gill openings 

 narrow. Anterior copula of hypobranchial cartilages segmented. Ventrals 

 small, below the pectorals. Tail distinct from the disk, narrow, tapering, 

 with a serrated spine in all the genera except Rhachinotus. Skin smooth or 

 rough with spines or tubercles or both. 



Tail long whip-like, without a serrated spine 



disk circular 



Tail long whip-like, with a serrated spine 



prepelvic process absent or rudimentary 

 disk quadrangular; tail filamentary 

 disk oval; tail compressed 

 Tail moderate to short, with a serrated spine ' 

 dorsal fin absent 



disk circular; caudal fins rayed, tail blunt 

 disk circular ; caudal fins rayed, tail pointed 

 disk subquadrangular, tail short 

 dorsal fin present 



disk of moderate breadth; tail short with rayed caudal fins 



Trygonoptera (page 409) 

 disk very broad ; tail tapering, pointed . . Aetoplatea (page 4:11) 

 dorsal fin absent 



disk very broad; tail short, slender, pointed . Pteroplatea (page 412) 



Rhachinotus (page 373) 



Dasybatus (page 375) 

 Taeniura (page 398) 



Urobatis (page 401) 

 Urotrygon (page 404) 

 Urolophus (page 407) 



Rhachinotus. 



Gymnura Muller & Henle, 1837, Sitzb. Akad. wiss. Berlin, p. 117. 



Urogymnus Muller & Henle, 1837, Wiegm. arch., p. 400; 1838, Charlesworth's mag., 2, p. 90; Gunth., 



1870, Cat. fishes Brit, mus., 8, p. 471. 

 Anacanthus Muller & Henle, 1837, Sitzb. Akad. wiss. Berlin, p. 117; 1838, Charlesworth's mag., 2, 



p. 90; 1841, Plagios., p. 156. 

 Rhachinotus T. Cantor, 1849, Malay fishes, p. 422. 



^ 



