FLOUNDERS OF GENUS PARALICHTHYS AND RELATED GENERA 



283 



mens none of tlie sti'uctural cliaracU'rs of wliicli 

 are decisively like their species. As examples of 

 the latter, we may cite the case of two specimens 

 from North Carolina here included with alhigntta. 

 One has D. 84, A. 63, the other D. 85, A. 62. 

 The gill rakers in both are 111 + 2. It may be 

 readily seen that so far as these characters are 

 concerned, they may equally as well be referred 

 to lethostigma. The number of scales is 54 and 

 53, respectively, this cliaracter being near the 

 mode of alhigutta, but it also falls at the extreme 

 of variation of lethontigmn. The two specimens, 

 howe\er, have the typical color pattern of al- 

 bigutta, and it is evident that they are extreme 

 specimens of that species witli respect to the fin 

 ray counts. A similar specimen from Cedar 

 Keys, Fla. (U.S.N.M. 35085), likewise has all the 

 structural characters examined close to the border 

 line between lethostigma and aJhigutta^ namely, D. 

 82, A. 63, gill rakers 2+ 11, scales 55, but the color 

 pattern is strongly marked and, without a doubt, 

 that of an olhigufta. The last specimen is also 

 of a size at which these two species show consid- 

 erable differences in jjroportional measurements: 

 length 376 mm.; depth 40.9; head 28.9; maxillary 

 15.3; inteiorbital 3. Comparing these measure- 

 ments with those given in table 8 for specimens of 

 similar size, it is found that they fall outside tlie 

 range of lefhosfigiiui — the depth decidedly so — 

 and within that of alblgutta. 



The preceding three specimens at the border 

 line between alhigutta and lethostigma showed 

 the characteristic color pattern of the former 

 sharply marked and could be placed with as- 

 surance in that species. Tlie situation is more 

 difficult when a similar border line specimen lacks 

 ocellated spots. The question then may arise: 

 Is it a h'thofitigma because of the lack of such spots, 

 or is it an individual variant of alhigutta with 

 respect to color, since occasional specimens of the 

 latter species, especially dark individuals, have 

 the spots very faint ? One such specimen from 

 North Carolina was examined: it has I). 81, A. 63, 

 scales 57, total number of gill rakers 12, and 

 lacks ocellated spots. Every one of these im- 

 poitant structural characters is about intermedi- 

 ate between alhigutta and lethostigmu and charac- 

 teristic of neither species. The color is like 

 lethofitigma, but it may possibly be an indiviilual 

 variant of (ilhigiifta. This specimen, 3;j0 nun. 



long, was placed with hthoxtigiiui on the basis of 

 its proportional measurements, namely, depth 

 4(i.5, head 27.1, interorbital 3.4. Comparing these 

 nu-asurements witli those given in table 8 for 

 the group of specimens of similar size, it may be 

 seen tiuvt the depth falls decidedly outside the 

 range of alhigutta and near the outer extreme 

 of lethostigma. The head measurement also falls 

 within the range of lethostigma and outside that 

 of alhigutta, but very near that of the latter. The 

 color agrees with that of lethontigma. 



By following the methods outlined, it was thus 

 possible to place individual hsh near the border 

 line with their respective species. Out of a total 

 of nearly 400 specimens studied in detail, only 

 one was found, the last one described, about wliich 

 some shade of doubt exists, and this is because 

 specimens of similar size were not available in 

 suflicient number to determine with entire assur- 

 ance the difference in measurements. Even as- 

 suming that it is a doubtful specimen — which it 

 hardly is — the proportion of doubtful s]iecimens, 

 one out of nearly 400, is low, probably less than 

 is usually the case among closelj- related species. 



It may be suggested that this last specimen is a 

 hybi'id, but this would be a mere assumption al- 

 though within the realm of possibility. While 

 some of the border-line specimens disctissed in the 

 preceding paragraphs maj- possibly lie hybrids 

 (p. 321), it would be necessary to make a much 

 more detailed study to be able to identify any hy- 

 briil specimens with reasonai)le assurance. At any 

 rate, it seems evident that hybrid specimens of 

 these flounders, if present, are comparatively few 

 in nature. The above placement of tlie border 

 line specimens apparently is in accord with their 

 sjiecitically genotypic origin, excejit a very few 

 possible hybrids, the existence of which it is not 

 possible to prove definitely at present. 



While the three common eastern sjiecies may be 

 distinguished reatlily even to imlividual fish, soon 

 after the rays and gill rakei-s become differentiated, 

 in fish of about 15 nun., this is not the case with 

 two common and geographically adjacent species 

 of the west coast, namely, calif ornicus and afstua- 

 rius (p. 30S). Small specimens, up to about 175 

 mm., of these two species are sometimes not pos- 

 sible to place with confidence. The two west coast 

 species differ also in the frequency distributions of 

 the numbers of (in ravs, biU there is more inter- 



