848 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.xxiii. 



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Giinther that the Leptocephalid forms are probal)ly "' individuals j 

 arrested in the development at a ver}' early period of their life, 3'et ' 

 continuini>- to grow to a certain size, without corresponding- develop- , 

 raent of their internal organs, and perishing without ha\ing attained fl 

 the charact(M"s of the })erfect animal." Tln^ recent observations of Dr. 1 

 Gilbert on the larvae of Alhula^ J^lojis, and C(m(/n\ however, seem to 

 point to the conclusion that these curious forms are normal young, 

 and that the individuals grow smallei' in size for a time with increased 

 age, owing to the increasing c-ompactness of the tissues. 



Inasmuch as the name Leptocephalus has been associated for more 

 than a century with larval forms, it is a decided inconvenienci^ to accord 

 to it precedence as a generic name over (^(»i<jer. The strict law of pri- 

 ority, however, demands its retention, and the tendency among syste- 

 matic zoologists is to recognize as f(nv exceptions as may ))e to this 

 rule. The unfamiliar names O.ri/nnis atid /AV////r^/.s- are l)oth earlier 

 than (hmjer. {XenToz^ slender; KfifxxXij, head.) 



The species of this genus are very difficult to determiiu\ Among 

 those found in flapan four are mujucstionably valid iin/r!a-'<ti i\ japonl- 

 cus^ nystroiiii, and retrotinctu,'<, but the other three may f)e forms of 

 japonicus. 



a. Lateral lini' with each pore in the center of a whitish spot, these close set, as wide 

 as the interspaces; about 38 before vent; head above with cross-series of many 

 white pores, obscure in the young; adult with a series of round, wide-set whitish 

 spots on each side of back; lower jaw included; pectoral more or less dusky, 

 the dorsal inserted nearly above its tip; dorsal and anal with broad l)lack mar- 



gni iiniri((sf<'r. 7. 



aa. Lateral line without pale dots or with them very inc-onspicuous, not so broad as 



the interspaces; head with cross-series of conspicuous pores, the pores uncol- 



ored, like pin pricks; no pale spots on sides of back. 



b. Dorsal tin beginning over or behind tij) of pectoral; pores before vent about 40; 



maxillary reaching posterior border of pupil; pectorals chiefly black; dorsal 



and anal witfi broad l)lack margin. 



<■. Ileail, 1:] in trunk; head and trunk, 1:| in tail cn'be)nni>^. 8. 



cr. Head, 1^ in trunk; head and trunk, 1 2 in tail k-iiiHii(aniis. 9. 



d. Pectorals pale; dorsal and anal with very little black margin or none; head 



and trunk, 1§ in tail jajxiiucK.s. 10. 



bb. Dorsal tin beginning nearly over middle of i)ectoral; dorsal and anal with broad 

 black margins. 



e. Dorsal and anal each with a broad margin for their whole length. Mouth 

 large, the maxillary extending to posterior margin of eye; eye, 65 in 

 head; jaws subequal; tail twice length of rest of body; 36 whitish pores 

 in advance of vent; no white spots on sides of back; dorsal and anal 

 broadly edged with black; tail not wliite-edged; pectoral pale, the dor- 

 sal beginning al)ove its middle riuk-innnfis. IL 



n: Mouth moderate, the maxillary not extending l)ey()nd puj)il; pores before 



vent about 40; trunk very short, containing iiead 1^ times; lower jaw short; 



mouth small, the maxillary to below middle of eye, 3 in head. ./(v/.s/roH*/. 12. 



ft'. Dorsal and anal pale, the posterior portion for about the length of the 



head, jet black; pores of lateral line, wide set, about 30 before vent; 



pores minute; mouth small; j)ectorals jiale rt'lrutinctu.s. 13. 



