FISHERY BULLETIN: VOL. 75, NO 4 



studied from freshly caught and preserved speci- 

 mens. Larimus fasciatus has the most oblique 

 mouth (Figure 20 A) with the lower jaw projecting 

 strongly in front of the nonprotrusible upper jaw. 

 The maxilla (Figure 21A) is under the lateral 

 margin of the rostral fold and its anterior end is 

 firmly attached to the premaxilla and skull (der- 

 methmoid). As the mouth opens, the distal ends of 

 the premaxilla and maxillae push forward as the 

 lower jaw is lowered (Figure 20A'). The mouth 

 opens widely. Cynoscion regalis has a large 

 oblique mouth with the tip of the lower jaw project- 

 ing in front of the nonprotusible upper jaw ( Figure 

 20B). The anterior end of the maxilla is firmly 

 attached to the premaxilla and articulates with 

 the dermethmoid (Figure 21B). As the mouth is 

 opened, the posterior end of the premaxilla and the 

 lower jaw move forward (Figure 20B'). The mouth 

 opens widely. Bairdiella chrysoura has a similar 

 mechanism of jaw movement (Figure 20C), but 



the mouth is only slightly oblique with the lower 

 jaw about equal in length to the upper jaw (Fig- 

 ures 20C, 21C). Micropogonias undulatus has an 

 inferior mouth with the tip of the lower jaw en- 

 closed by the protrusible upper jaw (Figure 20D). 

 The anterior end of the maxilla is loosely attached 

 to the premaxilla (Figure 21D). As the mouth is 

 opened, the entire premaxilla and the lower jaw 

 move anteroventrally (Figure 20D'). The mouth 

 opens widely. Menticirrhus saxatilis and Leiosto- 

 mus xanthurus have a similar mechanism of jaw 

 movement but their upper jaws seem more pro- 

 trusible (Figures 20E', F'; 21E, F). Their gape is 

 small. In M. saxatilis, the mouth is inferior and the 

 lower jaw is enclosed by the upper jaw (Figure 

 20E). Leiostomus xanthurus also has a small in- 

 ferior mouth (Figure 20F) with a small gape. 



The mouth position indicates that Larimus fas- 

 ciatus, C. regalis, and B. chrysoura are pelagic 

 feeders (Figure 20A-C) and that Micropogonias 



B 



mn 



ETHMOID REGION 

 DENTARY 



PREMAXILLA 

 MAXILLA 



FIGURE 21. — Jaw bones involved in mouth opening in juveniles of six species of sciaenids: A. Larimus fasciatus; B. Cynoscion regalis; C. 

 Bairdiella chrysoura; D. Micropogonias undulatus; E. Menticirrhus saxatilis; F. Leiostomus xanthurus. 



680 



