744 BULLETIN 10 0, UNITED STATES NATIONAL MUSEUM 



Family PLOTOSIDAE 



Body elongate, well compressed, tail tapering. Head depressed. 

 Barbels 3 pairs, as maxillary, mandibniar, and mental. Lateral fold 

 at mouth corner may be extended as short barbel. Mouth subtermi- 

 nal. Teeth conic in jaws, sometimes absent above or mixed with 

 molars below. Nostrils well separated, front pair usually tubular, 

 either at front edge of upper lip directed up or forw^ard or perfor- 

 ating lip and directed downward; hind nasal slit behind maxillary 

 barbel. Lateral line more or less distinct, pores well separated. 

 Postanal dendritic organ sometimes present, function apparently un- 

 known. First dorsal above or behind pectoral origins, spine smooth 

 or serrated on both front and hind edges. No adipose dorsal. Sec- 

 ond dorsal long, with numerous rays and like anal joined with 

 pointed caudal. Pectoral with sharp, pointed, barbed, strong or 

 weak spine. Ventral rays 10 to 16. 



Marine catfishes, though some living in estuaries or rivers. They 

 are confined to the Indo-Pacific, largely when in the Pacific in its 

 western portion. 



ANALYSIS OF GENERA 



a'. Front nostril at front border of upper lip, directed upward or forward. 

 b^. Gill meml)ranes free from isthmus; second dorsal origin behind ventral 



origin Plotosus 



&^ Gill membranes united to isthmus ; second dorsal origin before or above 



ventral origin Cnidog'lanis 



o^ Front nostril perforates upper lip near its front border, directed downward ; 

 only front part of gill membranes confluent with isthmus ; second dorsal 

 origin before or above ventral origin Paraplotosus 



Genus PLOTOSUS Lacepede 



Plotosus LAcfipfeDE, Hist. Nat. Poiss., vol. 5, p. 128, 1803. (Type, Platystacus 

 anguillaris Bloch, monotypic.) 



Plotosis DuM^RiL, Zool. Analytique, p. 340, 1806. (Tj^pe, Platystacus anguil- 

 laris Bloch.) 



Plotoscus Lesson, "Voy. Coquillc, Zool., vol. 2, pt. 1, p. 132, 1830. (Type, 

 Platystacus anguillaris Bloch.) 



Plotosius ScHLEGEL, in Siebold's Fauna Japonica, Poiss., pts. 10-14, p. 228, 1846. 

 (Type, Platystacus anguillaris Bloch.) 



Body elongate, robust forward, strongly compressed laterally, tail 

 tapering. Head depressed, covered with thin skin, bluntly rounded 

 in front. Eyes small, superolateral, not covered by skin. Mouth 

 transverse. Thick lips covered with papillae or small folds. Jaws 

 with 8 barbels, maxillary with but one pair. Conic teeth in upper 

 jaw numerous, in mandible mixed w^ith molars, on vomer molar 

 like crescent. Nostrils far apart, anterior tubidar, erect or directed 

 forw^ard. Gill openings wide, membranes free from isthmus. Gill 

 rakers 28 to 30. Branchiostegals 9 to 13. Air vessel moderate, not 



