I 



DESCRIPTION OF A NEW SPECIES OF THREADFIN 

 (FAMILY POLYNEMID^) FROM JAPAN. 



By David Starr Jordan and Richard Crittenden McGregor, 



Of Stanford [hiiremitij, California. 



Ill thi.s paper is uiven an account of the sing-lc species which repre- 

 sents in Japan the tropical family of Poli/nemidce. or Threadfins. 



Family POLYNEMID.E. 



Body oblong, compressed, and covered with nltlier large, loosely 

 inserted, ctenoid scales. Lateral line continuous, continued on the 

 tail, usually forked, with a branch on each lobe. Head entirel}^ scaly ; 

 snout more or less conical, projecting over the mouth, which is rather 

 large, inferior, with lateral cleft; premaxillary protractile, its basal 

 process vertical; maxillary without supplemental lione, extending 

 much beyond the eye, which is anterior, lateral, rather large, with a 

 well-developed, adipose eyelid. Villiform teeth on jaws, palatines, 

 and sometimes on vomer. Pseudo-branchif\? concealed. Branchioste- 

 gals 7. Gill membranes separate and free from the isthmus. Gills, 4, 

 a slit behind the fourth. Two separate dorsals, somewhat remote from 

 each other, the tirst of 8 feeble but rather high spines, the tirst and 

 last spines very short, the third longest; the second dorsal ecjual to 

 tii-st in height,-but base somewhat longer, of soft rays only. Annl Hn 

 either similar to or much longer than soft dorsal; caudal tin rather 

 long, widely forked. Second dorsal, anal, and caudal tins more or less 

 covered with small scales; the first 3 or 4 dorsal spines winged. Ven- 

 trals I, 5, abdominal, but not far removed from pectorals; pectoral 

 tins moderate, placed low, in two parts, the lower and anterior portion 

 of several tiliform articulated appendages, free from each other, used 

 as organs of touch. In the young the dorsal, caudal and pectoral Hns 

 are dusky, the anal and ventral tins white; all the fins grow darker 

 with age, the pectorals usually becoming black, the operculum blackish. 

 Bones of the skull with a well-developed nuu-iferous system as in 

 Sciwnidffi. Basis cranii double, with muscular tube; post-temporal 



Proceedings U. S. National Museum, Vol. XXX-No. 1470. 



813 



