148 MEMOISS OF THE QUEEN SLANT) MUSEUM, 



TRACHINOTUS Lacepede. 



Trachinotus Lacepede, Hist. Nat. Poiss., iii, 1802, p. 79 (Jalcatus) ; Jordan & Evermann, Fish. 

 North & Mid. Amer., pt. i, 1896, p. 939. 



Ccesiomorus Lacepede, ibid., p. 95 (bailloni). 



Acanthinion Lacepede, ibid., iv, 1802, p. 500 {rhomhoides = Jalcatus). 



Baillonus Rafinesque, Anal. Nat., 1815 (bailloni). 



Doliodon Girard, Proc. Acad. Nat. Sci. Phila., 1858, p. 168 {carolinns). 



BothroloimVrS Holbrook, Ichth. South Carolina, 1860, p. 82 (pampanus = carolinus). 



Trachynotus Giinther, Brit. Mus. Catal. Fish., ii, 1860, p. 480 ; amended orthography. Pre- 

 occupied in Coleoptera by Latreille in 1829 and in Hymenoptera by Gray 1829. 



" THE SWALLOWTAILS." 



Body ovate or elevated, more or less strongly compressed ; abdomen 

 rounded, shorter than the anal fin. Scales small, smooth, and adherent, covering 

 the breast. Lateral line complete, straight or but little curved, sometimes locally 

 undulous. Head rather small, with moderate, truncate or rounded snout, 

 scaleless or partially scaly. Mouth protractile, with rather small, horizontal or 

 slightly oblique cleft, the jaws subequal; maxillary without distinct supplemental 

 bone. Jaws, vomer, and palatines with bands of villiform teeth, disappearing 

 usually with age. Opercles entire in the adult, the young with strong preoper- 

 cular armature. Two dorsal fins, the first of 6 or 7 spines with an anterior 

 procumbent spine ; in the young the former are connected by membrane, but with 

 advancing age this gradually disappears leaving each free, while in very old 

 examples even these are absorbed ; soft dorsal and anal fins similar in form and 

 size, the anterior rays in each more or less produced; two stout semi-detached 

 spines in front of the anal, disappearing with age. Caudal deeply forked. 

 Pectoral small, with 17 or 18 rays, the upper the longest. Ventrals small and 

 close together, with i 5 rays, inserted below or behind the base of the pectorals. 

 Gill-openings wide; gill-membranes separate, free from the isthmus; branchios- 

 tegals seven; pseudobranchia} present, concealed in old examples; gill-rakers in 

 moderate number, well developed or short; pharyngeal bones strongly armed 

 in the young, the teeth caducous; third upper pair and lower pair closely in 

 contact but not united, (rpaxrs, rough; vwro?, back.) 



Carangoid fishes of moderate or large size, inhabiting all warm seas ; about 

 25 valid species. 



Remarkable changes of form and structure take place in these fishes 

 between youth and age. Very young examples have the angle of the preopercle 

 armed with 3 strong spines, and the limbs, both vertical and horizontal, more 

 feebly denticulated; the jaws, vomer, palatines, and pharyngeals toothed; and 

 the spinous dorsal developed as a normal fin. In the second, or Doliodon, stage 

 the preopercular spines have been absorbed into the body of the bone, and the 

 relative values of the spinous and soft dorsal fins undergo a reciprocal change, 

 the decrease in the former being counterbalanced by a corresponding increase 

 in the latter. When the half-grown, or Trachinotus, stage has been reached, 

 the connecting membrane between the dorsal spines has disappeared, and the 

 functional value of the teeth has perceptibly diminished. In the last, 

 Bothrolcemus, stage the teeth both of the mouth and the gullet, the pseudo- 

 branchiae, and the si)inous dorsal and anal fins have quite disappeared, while 

 the lobes of the soft dorsal, anal, and caudal fins have attained their maximum 

 development. 



