442 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 



early i^eriod the preoperciilar spines are absorbed into the substance of 

 the preoperculum and disappear. The spinous dorsal and the teeth are 

 still retained. In this condition it remains for some time, "^he spinous 

 dorsal, however, gradually losing its relative size, while the soft vertical 

 fins increase. In this stage the species belongs to the genus Doliodon 

 of Girard. At a later period the membrane connecting the dorsal spines 

 has become obsolete, and the species then rejireseuts the genus Trachy- 

 notus, as understood by Cuvier and Valenciennes, and others. Finally, 

 in old age, the teeth of the jav^^s, palate, and i^haryngeal bones have fallen 

 out, and the lobes of the dorsal, anal,, and caudal fins attained their 

 greatest extension and become pointed. This final stage has been made 

 known by Holbrook under the new generic name of Bothrolcemus^^ (Grill, 

 Proc. Acad. Nat. Sci. Phila. 1862, 440). The pseudobranchiae also dis- 

 appear in old specimens. T!he species of Trachynotus are among those 

 most highly valued as food-fishes, (jpa/,^^, rough 5 '^wtu^^ back.) 



a. Body without dark bauds. 



b. Vertical fins without black. 



696. T. caroMaiBJS (L.) Gill. — Common Pompano. 



Uniform bluish above, sides silvery, golden in the adult, without 

 bands; fins plain silvery or dusky. Body oblong ovate, elevated, pro- 

 file forming a gentle curve from the middle of the back to the snout, 

 where it descends abruptly. Dorsal and anal falcate, their lobes reach- 

 ing when depressed nearly to the middle of the fin ; pectoral reaching to 

 opioosite the vent. Gill-rakers short, slender in the young, becoming 

 thick in the adult. Head 4; depth 2^. D. VI-I, 25 j A. H— I, 23. L. 

 18 inches. West Indies, north to Cape Cod; the most valued food-fish 

 of our southern waters. 



{Gastcrosteus caroVmus Linn. Syst. Nat.: Trachynotus pampaniLS Giinthor, ii, 484; 

 Bothrolccmu'S pampanus Holbrook, Ichth. S. C. 1860, 81.) 



hh. Vertical fius largely black. 



69?'. T. ovatMS (L.) Gthr. 



Bluish, sides silvery; lobes of the dorsal and anal more or less black. 

 Body comparatively deep. Head about 4. Depth If to 2. D. VI-I, 

 19 ; A. II — I, 18. In all warm seas ; north to Virginia on our Atlantic 



coast. 

 {Crasterosfeus ovatus L. Syst. Nat.; Giintlier, ii, 481.) 



698. T. g^oi ecnsBS C. & V. 



Dorsal, anal, and caudal lobes black. Snout obliquely truncated; 

 maxillary reaching to below the centre of the eye; anterior rays of dor- 



