408 Bulletin 47, United States National Museum. 



gg. Mouth moderate, terminal, the maxillary of about three pieces ; stomach 

 not gizzard-like. CLTJPEID^E, LXI. 



ggg. Mouth subinferior, very large, below a tapering, pig-like snout ; maxil- 

 lary very long. ENGRAUUDID;E, LXII. 

 bb. Dorsal fin posterior, opposite anal ; deep-sea fishes, of loose organization ; mostly 

 blackish in color ; mouth small, with small pointed teeth ; air bladder wanting. 



ALEPOCEPHALID^:, LXIII. 

 SAIMONIDEA : 

 aa. Adipose fin well developed ; oviducts none, the large eggs usually falling into the cavity 



of the abdomen before extrusion ; air bladder well developed. 

 1i. Stomach siphonal, not having the form of a blind sac ; pyloric cceca many ; branchios- 



tegals rather numerous. 



i. Parietals separated by the supraoccipital ; dorsal fin moderate, the simple rays in 



front few in number. SALMONID^, LXIV. 



ii. Parietals in contact, not separated by a supraoccipital ; dorsal fin very long and 



high, the simple rays in its anterior half very numerous. THYMALLID^E, LXV. 



hh. Stomach coecal, of the form of a blind sac ; pyloric cceca generally few. 



j. Branchiostegals 6 or more ; gill membranes separate. ARGENTINID*:, LXVI. 



jj. Branchiostegals 3 or 4 ; body subterete ; mouth small. MICHOSTOMID^;, LXVII. 



Family LVI. ELOPID^. 



(THE TARPONS.) 



Body elongate, more or less compressed, covered with silvery, cycloid 

 scales ; head naked. Mouth broad, terminal, the lower jaw prominent. 

 Premaxillaries not protractile, short, the maxillaries forming the lateral 

 margins of the upper jaw ; maxillary composed of about three pieces, 

 extending backward beyond the eye ; an elongate bony plate between the 

 branches of the lower jaw (analogous to the gular plate in Anna *) ; bands 

 of villiform teeth in both jaws and on vomer, palatines, ptefygoids, 

 tongue, and base of skull ; no large teeth. Eye large, with an adipose 

 eyelid. Opercular bones thin, with expanded membranaceous borders; 

 a scaly occipital collar. Gill membranes entirely separate, free from the 

 isthmus. Branchiostegals numerous, (29 to 35). Gill rakers long and 

 slender. Pseudobranchise present or absent. Belly not keeled nor serrated, 

 rather broad and covered with ordinary scales. Lateral line present. 

 Dorsal fin inserted over or slightly behind ventrals ; caudal fin forked; no 

 adipose fin; dorsal and anal depressible into a sheath of scales; pectorals 

 and ventrals each with a long accessory scale. Parietal bones meeting 

 along top of head. Pyloric cceca numerous. Genera three, species about 

 five, forming two well-marked subfamilies, both widely distributed in the 

 tropical seas. The species are not much valued as food, the flesh being 

 dry and bony. (Clupeidce, group JSlopina, Giinther, Cat., vn, 469-471, 1868.) 



MEGALOPINJE : 



a. Pseudobranchiae none ; body oblong, covered with large scales ; anal fin larger than dor- 

 sal ; last ray of dorsal produced in a long filament. 



b. Dorsal fin inserted notably behind insertion of ventrals. TARPON, 197. 



ELOPING: : 



aa. Pseudobranchiaj large ; body elongate, covered with small scales ; anal fin smaller than 

 dorsal ; last ray of dorsal not produced in a filament. ELOPS, 198. 



*The gular plate suggests the similar structure seen in Amia, but its homology is not proved. 

 Although the Glupeiform fishes are probably descended from Ganoids related to Amia, there may 

 be no closer relation between Amia and Slops or Megalops, than between Amia and Clupea. 



