28. AMIID^. 93 



and very bard, scarcely covered by skin. Snout sliort, rounded. Lat- 

 eral margins of upper jaw formed by the maxillaries, wbich are divided 

 by a longitudinal suture. Jaws nearly even in froQt. Cleft of the 

 mouth nearly horizontal, extending beyond the small eye. Lower jaw 

 broad, U-shaped, the rami well separated. Between them a broad bony 

 l)late, with radiating stride, its posterior edge free. Jaws each with an 

 outer series of conical teeth, behind which in the lower is a band of 

 rasp-like teeth. Bands of small teeth on the vomer and pterygoids. 

 Palatines with a series of larger, pointed teeth. Premaxillaries not pro- 

 tractile. Tongue thick, scarcely free at tip. Nostrils well separated, the 

 anterior with a short barbel. Suborbital very narrow. A bony plate 

 covering the cheek, similar to the plates on the toi^ of the head. Oper- 

 culum with a broad dermal border. Branchiostegals 10-12. No pseu- 

 dobranchise nor opercular gill. No spiracle. Gills 4, a slit behind the 

 fourth. Gill membranes not connected, free from the isthmus. Two 

 peculiar, long, lanceolate, obliquely striate appendages on each side 

 of the isthmus, projecting backward and covered by the branchioste- 

 gal rays, the anterior wholly adnate to the isthmus, the posterior 

 free behind.* Isthmus scaleless. Gill-rakers stoutish, very short. 

 Scales of moderate size, rather firm, cycloid, with a membranaceous 

 border. Lateral line present. Dorsal fin long and low, nearly uniform ; 

 the posterior rays not much higher than the others; its insertion in 

 front of the middle line of the body, opposite the end of the i)ectoral. 

 Tail somewhat heterocercal (more so in the young), convex behind. No 

 fulcra. Anal fin short and low. Pectoral and ventral fins short and 

 rounded, the ventrals nearer anal than pectorals. Vertebrae amphicoe- 

 lian, as usual among'fishes. Abdominal and caudal parts of the ver- 

 tebral column subequal. Air-bladder cellular, bifid in front, lung-like, 

 connected by a glottis with the liharynx, and capable of assisting in 

 respiration. Stomach with a bliud sac 5 no i)yloric coeca. No closed 

 oviduct. Intestine with a rudimentary spiral valve. Fresh waters of 

 the United States. A single species known. 



* See Wilder "On the Serrated Ajjpendages of the Throat of Amia," Proc. Amcr. 

 Assoc. Adv. Sci. 1876, 259, for a discussion of these curious organs. 



