A REVIEW OF THE PCECILIID.E OR KILLIFISHES OF 



JAPAN. 



By David Starr Jordan and John Otterbein Snyder, 



Of Slaiiford University, California. 



In this paper i.s given a review ot" the species of Pwciliidse or 

 Gyprinodimtklix,^ found in the waters of Japan. But two species are 

 recorded, both fishes of very small size, living in pools and ditches in 

 the rice swamps of southern Japan, and doubtless feeding on moscjui- 

 tos. The specimens examined were collected by the authors during 

 1900. The}^ are in the United States National Museum and in the 

 museum of Stanford University. 



Family PCECILIIDyE. 



Body oblong or moderately elongate, compressed behind, depressed 

 forward, covered with rather large c3'cloid scales, which are adherent 

 and regularl}^ arranged. Lateral line wanting or represented by a few 

 imperfect pores. Head scaly, at least above. Mouth terminal, small, 

 the lower jaw usually projecting; margin of the upper jaw formed by 

 the prcmaxillaries only; premaxillaries strong, extremely protractile. 

 Teeth incisor-like or villiform, sometimes present on the vomer, but 

 usuall}' in the jaws only; lower phar3'ngeals separate, with cardiform 

 or rarely molar teeth; third upper pharyngeal enlarged, the fourth 

 wanting or united to the third. Gill membranes somewhat connected, 

 free from isthmus; gill rakers very short, thick. Branchiostegals 4 

 to 6. Pseudobranchiie none. Dorsal iin single, inserted posteriorly, 

 of soft rays only, rarely with a single spine or a rudimentary spinous 

 dorsal; caudal fin not forked; ventral fins abdominal, rarely wanting; 

 pectoral fins inserted low; no adipose fin. Stomach siphonal, without 

 ])yloric appendages. Air bladder simple, often wanting. Basis cranii 

 simple. Sexes usually unlike, the fins being largest in the male, but 

 in some species the females are much larger in size. Many of the 

 species are ovoviviparous, the .young well developed at time of birth. 

 In these species the sexes are very unlike, the anal fin of the male being 



Proceedings U. S. National Museum, Vol. XXXI— No. 1486. 



287 



