44 OSTEOLOGY OF SCOMBROID FISHES 



The Branchial and Hyoid Arches. 



There are three tooth-bearing superior pharyngeals on each side of 

 the last three arches, and a styliform naked one on the first arch in 

 all of the forms here considered. The first toothed pharyngeal is 

 elongate and lies in front and along the outer edge of the second. The 

 second is always the largest; the third is directly behind it and rather 

 closely joined to it, so that they together form an elliptical plate. The 

 teeth on both the superior and inferior pharyngeals of Elagatis, Oligo- 

 plites and Naucrates are fine and sharp. In the others some, or nearly 

 all, of the teeth are blunt molar teeth, particularly on the second 

 toothed superior pharyngeal and along the middle of the inferior 

 pharyngeal. 



The inferior pharyngeals lie close together along their inner edges 

 for the greater part of their length and widely diverge posteriorly. In 

 Elagatis, Naucrates, Scomberoides and Oligoplites they are less closely 

 attached than in the others. 



Trachinotus is an exception to all of the foregoing pharyngeal 

 characters. In this genus the pharyngeals are developed to a remark- 

 able size. In the largest skeleton (T. kennedyi, 24 inches long) the 

 first toothed pharyngeal is so reduced as to be practically f unctionless ; 

 it is y of an inch wide and half as long. The second is greatly en- 

 larged, being 1% inches long by half as wide, and % of an inch thick. 

 The third is 7/16 of an inch wide by 3/16 of an inch long. Each 

 inferior pharyngeal is 2 inches long by half as wide and % of an inch 

 thick. The first superior pharyngeal lies at the outer side of the sec- 

 ond, considerably behind its front end, while the third is at the 

 posterior end of the second and does not enter into its outline as in 

 the other forms. The inferior pharyngeals and the second toothed 

 pharyngeals of opposite sides meet at the median line and are closely 

 joined to each other, each pair forming an equilaterally triangular 

 plate, so closely joined as to form an almost unbroken surface from 

 side to side. In the superior pharyngeals the triangular shape is less 

 evident, as the outer angles are broadly rounded. The inferior plate is 

 shallowly concave, and the superior correspondingly convex. Except at 

 the anterior end the plates are covered with a smooth pavement, as if 

 the bone, or close-set teeth, had been ground down to a common level. 

 The anterior parts are deeply pitted. 



In the young the tooth plates are scarcely so thick correspondingly, 

 and they are pitted all over the grinding surfaces. These bones are 

 apparently not of the same character as the bones that thicken or swell 



