NO. 5 MYERS AND WADE : ATHERINID FISHES 123 



Ian (USNM 29243) is in good enough condition to show these charac- 

 ters clearly ; and, until a large, finely preserved sample of specimens from 

 Mazatlan is available, it would be useless to speculate upon the systematic 

 characters and possible racial relationships of the population at the type 

 locality of eriarcha. 



An effort was made to correlate these elusive characters of the Lower 

 California and Oaxaca series with the more usual types of counts and 

 measurements used in defining systematic units in fishes; but, although 

 these do in part support the differences observable "by eye," the varia- 

 tions encountered are so great, so haphazard, and so unexpected that we 

 have been forced to conclude that a racial analysis of the populations of 

 Eurystolc eriarcha must await the collection of large series well repre- 

 senting the range of the species — from the Gulf of California and the 

 Revillagigedo Archipelago to the coast of Colombia. It must be remem- 

 bered that the available material is almost all from at or near the north- 

 ern and southern extremes of the supposed range of the species. 



The counts and proportional measurements of the Oaxaca and Lower 

 California (Arroj'o de San Luis) series are presented in Table L 



The two rather peculiar specimens which were mentioned above (one 

 from the Arroyo de San Luis and one from the Oaxaca series) differ 

 rather strikingly from the others. The Lower California specimen, 54.5 

 mm in standard length, besides entirely lacking the dark scale-edgings 

 of the dorsum and most of the supraocular and snout pigmentation, dif- 

 fers from its fellows in the greater depth. Moreover, the extended line 

 of the upper edge of the lateral band subtends the upper edge of the 

 orbital rim. The peculiar Oaxaca specimen (40.5 mm in standard length) 

 resembles its fellows and the peculiar Lower California example in its 

 lack of dark pigmentation, but, unlike the other Oaxaca specimens, the 

 head axis is in line with the body axis. In both of these peculiar specimens, 

 and in contradistinction to nearly all the others in both series, the anterior 

 part of the lateral silvery band is curved noticeably upward. The shape 

 of the head of the Lower California individual mentioned also appears 

 peculiar, but this is due solely to the unnatural extension of the branchi- 

 ostegal membranes. This same fortuitous peculiarity is shown also in 

 Jordan's 1895 plate of Nectar ges nepenthe. 



Dr. L. P. Schultz has given us the following counts and measure- 

 ments of the holotype of E. eriarcha (USNM 29243) : standard length 

 35.5, head length 8.8, body depth 7.8, eye diameter 3.9, length caudal 

 peduncle (base of last anal ray to end of hypural fan) 7.2, least depth 



