270 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



gill rakers, fin rays, and scales. As these numbers 

 vary within wide limits within the species, and 

 individual fish of closely related species may ap- 

 proach or even overlap in these respects, it is 

 evident that the course of the student in his at- 

 tempt to properly distinguish the species is beset 

 with many pitfalls. By way of illustration, it may 

 be pointed out that a specimen of lethostigma, for 

 instance, having 65 rays in the anal fin may be con- 

 sidered as conspecific with a specimen of alh'tgutta 

 having 62 rays, rather than with another specimen 

 of h-thoxtiyma having 72 rays, as far as this one 



character is concerned. Of coui-se, in the proper 

 identification of any given specimen all the char- 

 acters must be taken into account, but the student 

 will be greatly aided in reaching the correct con- 

 clusion, if instead of the simple range of each 

 meristic character, he has before him tables show- 

 ing the frequency distributions of these charac- 

 tei-s. Such tables are therefore supplied here, as 

 far as availal)le material permitted. In addition 

 to their practical value, the tables afford valuable 

 evidence going to prove the distinctness of closely 

 related species, where doubt may exist. 



Table 1. — Fiequencii fHntribiitimi hi/ number of ohliqiie rovs of scales over straight part of lateral line to end of hypiiral. 



Number of scales 



SCALES 



The cycloid or ctenoid character of the scales is 

 of primary importance in the major division of the 

 species comprising the genus Paralichthys and is 

 of much help in the identification of the species 

 of this genus as well as of related genera. In the 

 Fishes of North and Middle America, by Jortlan 

 and Evermann (Bull. U. S. Nat. Mus., No. 47, Pt. 3, 

 1898), a general work used by ichthyologists to 

 identify American fishes, this character is inade- 

 quately treated. In the definition of the genus 

 (ibid. p. 2624) the statement is made "scales small, 

 weakly ctenoid or ciliated." This is not true of 

 all the species ; and in the descriptions of some of 

 the species the scales are correctly described as 

 "smooth" or "cycloid." It is interesting to note 

 that in the same work, the two genera which are 

 closely related to Paralichthys^ namely, Hip- 

 poglossina (p. 2020) and Lioglossina (p. 2()2'2), 

 as limited by those authors, are distinguished by 



the scales, ctenoid in one and cycloid in the other. 

 This character is also of importance in forming 

 major divisions of the species comprising the 

 genus Paralichthys. The presence or absence of 

 s])iiiules on the scales was found to be the most con- 

 stant of all characters used in the distinction of 

 the species, with the exception of P. assfuarius and 

 Hippoglossina oblonga (the latter species being 

 assigned to Paralichthys by Jordan and Evermann 

 in the work cited). In H. oblonga the number of 

 spinuliferous scales is highly variable, but a few 

 are always present on the caudal peduncle of the 

 blind side in specimens over 75 mm. long, and the 

 eyed side of the head always has spinuliferous 

 scales in large specimens. In P. aestiuirius, it is 

 an age character, the scales of the eyed side being 

 all si)inuliferous in fish less than about 160 mm. in 

 length. The spinules are gradually lost after 

 that length has been reached; the scales become 

 cycloid in specimens over 220 mm. In the other 



