Jordan and JKvermann. Fishes of North America. 831 



body elongate, compressed, outline from spinous dorsal to snout slightly 

 convex, and little declined. Head much longer than high ; snout conical, 

 7 in head; eye rather large, about 5 in head. Scales of small size. 

 Longest dorsal spine If in head ; longest ray of soft dorsal If in head ; 

 caudal lobes slightly longer than head; pectoral fin as long as head 

 behind pupil; pectoral filaments 8 or 9, reaching near front of anal fin in 

 adult. Color greenish brown above and yellowish green below. Pacific 

 Coast of tropical America, generally common from Cape San Lucas to 

 Panama, (opercularis, from the dusky blotch on the operculum, found 

 also in most other species.) 



Trichidion opercnhiris, GILL, Proc. Ac. Nat. Sci. Phila., 1863, 168, Cape San Lucas. 

 Poli/m-mm melanopoma, Gi'NTHER, Fish. Centr. Amer., 421, 1869, San Jose de Guatemala. 

 Polynemns opercularis, STEINDACHNER, Ichthyologische Beitrage, iv, 9, 1875; JORDAN & GILBERT, 

 Bull. U. S. Fish Comrn., n, 107, 111, 1882; JORDAN, Proc. U. S. Nat. Mus., 372, 1885. 



Group AMMODYTOIDEI. 

 (THE SAND LAUNCES.) 



This group, consisting of the single family Ammodytldm, is of unknown 

 relations. It has been usually placed among the OpMdioid forms, with 

 which it agrees in the long dorsal and anal fins destitute of spines. In 

 the character of its mouth and gill structures it resembles the Atherinidce 

 rather than the Ophidioidei. The ventral fins are wanting. Our knowl- 

 edge of the anatomy of Ammodytes is still incomplete and gives no 

 certain clue to its relationships. The family is placed by Jordan & Gil- 

 bert between the Percesoces and the Scombroidei. Knowing no better 

 place for it we leave it next the Percesoces. 



Family CX. AMMODYTID^E. 

 (THE SAND LAUNCES.) 



Body elongate, compressed, covered with small cycloid scales. Head 

 long. Mouth rather large, nearly horizontal, the lower jaw considerably 

 projecting, its symphysis produced. No teeth in jaws. Gill openings 

 very wide ; gill membranes not united, free from the isthmus. Branchi- 

 ostegals 6 to 8. Pseudobranchiae large, lamellate. Gill rakers long and 

 slender ; gills 4, a slit behind the fourth. Opercles well developed, with- 

 out spines or serratures. Eye moderate. Premaxillaries very protract- 

 ile. Maxillaries long and slender. Lateral line running along side of 

 back. Spinous dorsal absent; soft dorsal very long and low, fragile, 

 extending from behind the head to near the base of caudal. Caudal fin 

 small, forked. Anal similar to dorsal, but smaller. Vent inserted 

 behind middle of body. No ventral fins. Pectoral fins inserted low. 

 Lower pharyngeals very small, separate. No air bladder. Pyloric cosca 

 usually 1. Genera 3, Ammodytes, Hyperoplus, and BleeJceria ; one genus in 

 India; species about 10. Small carnivorous fishes, swimming in large 

 schools near the shore and burying themselves in the sand, along the 



