JORDAN AND THOMPSON: FISHES OBTAINED IN JAPAN IN 1911. 217 



This species is most closely related to Gnathopogon mayedce, from which it 

 may be at once differentiated by the longer barbel and the extension, when supine, 

 of the anal rays, more than half-way from the last anal ray to the first caudal ray. 

 Other differences are the scales enlarged in the middle line of the back, the presence 

 of one more series of scales above the lateral line, the slightly shorter distance from 

 the tip of the snout to the occiput, the longer ventrals, and deeper caudal peduncle. 



Among the cotypes are both males and females, with ripe gonads. The male is 

 distinguished from the females by the presence of a smooth overgrowth on the front 

 and sides of the snout. The eggs are small, as in others of the genus, being about 

 half a millimeter in diameter. As the female, which was taken as the type, is the 

 most strongly pigmented of any of the specimens, it is probable that the males are 

 not, as a rule, colored more highly than the females. 



Among the specimens recorded by Jordan and Snyder from Lake Biwa as 

 Leucogobio mayedce there are a number of specimens of this species, all of them very 

 small. Nos. 6009a-c Lake Biwa. 



This species is named for Pjofessor Chiyomatsu Ishikawa, of the Imperial 

 University of Tokyo, who early studied the fishes of Lake Biwa. 



Key to Japanese Species of Gnathopogon. 

 a. Anus distant but the breadth of one scale from first anal ray; pectoral extending less than two-thirds 

 of distance to ventrals; gill-rakers numerous, 4-|-9 or 10; body-depth 4. 

 6. Caudal peduncle deep, 8.5 in body; barbel long, three-fifths of diameter of eye; scales 36 to 38; 



pharyngeal teeth only occasionally and slightly serrate elongatus. 



bb. Caudal peduncle slender, about 10 in body; barbel short, one-fourth of diameter of pupil; scales 



42; pharyngeal teeth constantly and strongly serrate on grinding surface jordani. 



aa. Anus distant at least 2.5 scales from first anal ray (two-thirds of eye) ; pectoral extending more than 

 two-thirds distance to ventrals; gill-rakers short and rudimentary, 3 or 4-|-4, lacking anteriorly, 

 c. Depth 4 in body; anus 2.5 scales (two-thirds diameter of eye) distant from first anal ray. 



d. Scales in middle line of back enlarged; rows between lateral line and dorsal 3.5; anal rays 

 extending over half-way from base of last to first caudal rays; maxillary not reaching 



beyond orbit, its barbel under nostril; barbel two-thirds of eye ishikawm. 



dd. Scales in middle line of back not enlarged; rows between lateral line and dorsal 4.5; anal 

 rays not extending half-way to first caudal rays; maxillary reaching beyond orbit; its 



barbel short, less than pupil mayedce. 



cc. Depth 6 in body-length; anus distant the breadth of 4.5 scales (1.16 times diameter of eye) from 

 insertion of anal fin; 5 scales above lateral Une; barbel one-half diameter of eye; scales in 

 middle line of back but slightly enlarged gracilis. 



48. Acheilognathus rhombeus (Temminck & Schlegel). 

 Lake Biwa, at Matsubara, No. 6327 many. 



Capoeta rhombea Schlegel, Fauna Japonica, Poiss., 1846, p. 205, pi. C, fig. 6; near Nagasaki. 

 Acheilognathus rhombeus Bleeker, Prodr. Cypr., 1, 1860, p. 255. 



