Fishes of the Western North Atlantic 343 



serrate or pectinate adherent scales, the exposed part of which is much deeper than 

 long; the modified series of scales next to the median line of the back in front of the 

 dorsal fin; the very long gill rakers on the upper limb, which project downward 

 over the equally long rakers of the lower limb; the very deep cheek; and the rather 

 small pelvic, composed of only seven rays. 



The young, about 60 mm TL and less, of North American representatives at least, 

 have minute teeth on the margin of the maxillary, but these disappear with age. The 

 gill rakers on the upper limb do not yet extend downward over those on the lower limb, 

 as in larger fish; the number, as already indicated, increases greatly with age. Further- 

 more, until the fish reach about 100-125 mm TL, the two series of scales, one on 

 each side of the median line of the back in front of the dorsal fin, do not become fully 

 difTerentiated or modified. Though the exposed margin of the scales on young may 

 be somewhat uneven, the scales are not definitely serrate; the serrae become somewhat 

 developed when the fish attain a length of about 100 mm and continue development 

 until they are comparatively large, but these serrations are not developed uniformly 

 on all parts of the fish. For some species the length and shape of these serrations or 

 pectinations are diagnostic characters, but fish of nearly equal size must be compared 

 and scales from the same part of the body must be used. 



The species of Menhaden included in this work fall into two closely related pairs: 

 tyrannus from the Atlantic and patronus from the Gulf; smithi from the Atlantic and 

 gunteri from the Gulf — and one odd species, brevicaudata, from Noank, Connecticut, 

 related to tyrannus. Such a close relationship between species exists in other groups 

 as well.^^ 



In each pair of fishes named, the range probably was once continuous but became 

 discontinuous when the last passageway for marine fishes across the Florida peninsula 

 was closed. At least these fishes do not now occur on the coasts of southern Florida, 

 indicating that suitable conditions do not exist there. Therefore, the separation between 

 Atlantic and Gulf representatives is complete. Under this separation, and apparently 

 under the influence of differences in environment, these fishes have become sufficiently 

 differentiated to constitute distinct species. 



Range. The Atlantic and Gulf coasts of the United States northward to Nova 

 Scotia; southern Brazil to Argentina; and western Africa. 



Measurements and Counts for Brevoortia. For measurements and counts not dis- 

 cussed below, see p. 258. 



Head depth : for this genus, measured from the slight crossgroove at occiput to 

 the keel of the first ventral scute. Although this is not an exact vertical, it does 

 provide definite and uniform points for measuring. 



Scales; the number in a lateral series represents the number of oblique series 

 (running upward and slightly backward) across the middle of the side ; these should 



36. Among the shad, Alosa lapidissima of the Atlantic and A. alabamae of the Gulf; also the hickory shad, Pomolobus 

 mediocris, of the Atlantic and the skipjack herring, P. chrysockloris, of the Gulf and Mississippi Valley. In the 

 family Sciaenidae, the weakfish, Cynoscion regalis, of the Atlantic and the sand seatrout, C. arenarius, of the Gulf 

 (Ginsburg, 41: 83); and another pair occurs in the genus Menticirrhus (Ginsburg, unpublished). 



