FISH OF ONTARIO. 17 



by a longitudinal suture. Jaws nearly even in front ; cleft of the mouth 

 nearly horizontal, extending beyond the small eye; lower jaw broad, the 

 rami well separated ; between them a broad, bony plate, with radiating 

 stria% its posterior edge free; jaws each with an outer series of conical 

 teeth, behind which in the lower is a band of rasp-like bands of small 

 teeth on the vomer and pterygoids ; palatines with a series of larger pointed 

 teeth ; premaxillaries not protractile ; tongue thick, scarcely free at tip. 

 Nostrils well separated, the anterior with a short barbel ; suborbital very 

 narrow; a bony plate co\ering the cheek, similar to the plates on the top 

 of the head ; operculum with a broad dermal border. Branchiostegals ten 

 to twelve. No pseudobranchige nor opercular gill ; no spiracle ; gills, four, 

 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 branchio- 

 stegal 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 membranous 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 pectoral. Tail somewhat heterocercal 

 (more so in the young), convex behind, no fulcra. Anal few, short and 

 low. Pectoral and ventral fins short and rounded, the ventrals nearer 

 anal than pectorals. Vertebrae amphicoelian or double concave, as usual 

 among fishes, none of them specially modified. Abdominal and caudal 

 parts of the vertebral column subequal. Air bladder cellular, bifid in 

 front, lung-like, connected by a glottis with the pharynx and capable of 

 assisting in respiration. Stomach with a blind sac; no pyloric caeca. No 

 closed oviduct. Intestine with a rudimentary spiral valve. 



Only one species of this family is known among living fishes, but 

 several fossil genera are commonlv referred to it. 



Genus AMI A. (Bowfixs.) 



Body oblong, compressed behind, terete anteriorly ; head subconicai, 

 anteriorlv bluntish, slightly depressed, its superficial bones corrugated and 

 very hard, scarcely covered by skin; snout short, rounded; lateral margins 

 of upper jaw formed by the maxillaries, which are divided by a longitudinal 

 suture ; jaws nearlv even in front ; 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 plate, with radiating stria;, 

 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 protractile ; tongue thick, scarcely free at tip ; 

 nostrils well separated, the anterior with a short barbel ; suborbital very 



