90 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — IV. 



forming most of the margin of the npper jaw ; the maxillary transversely 

 divided into several i)ieces. Lower jaw composed of as many pieces as 

 in reptiles. Coronoid i^resent. Both jaws with an onter series of small 

 teeth, followed by one (or two) series of large teeth, besides which on 

 the jaws, vomer, and palatines are series of small, close-set, rasp-like teeth. 

 Tongue toothless. Large teeth of the jaws conical in form, pointed and 

 striate, placed at right angles to the jaw. These large teeth rest, accord- 

 ing to Agassiz, in a rather deep furrow, protected on the outside by the 

 raised border of the jaw, and on the inside by a ridge of the same 

 nature. These teeth are pierced in the centre by a foramen, which 

 communicates with the maxillary canal, and through which the nerves 

 and blood vessels enter the pulp cavity of the tooth. The forms of the 

 folded layers of dentine within the teeth are peculiar. Pharyngeals 

 with rasp -like teeth. Tongue short, broad, emarginate, free at tip. Ex- 

 ternal bones of skull very hard and rugose. Eyes small. Nostrils near 

 the end of the upper jaw. An accessory gill on the inner side of the 

 opercle. Pseudobranchiae present. 'So spiracles. Gills four, a slit be- 

 hind the fourth. Brauchiostegals 3. Gill membranes somewhat con- 

 nected, free from the isthmus. Gill -rakers very short. Air-bladder cellu- 

 lar, lung-like, somewhat functional, communicating by a glottis with the 

 oesophagus. Fins with fulcra. Dorsal fin short, rather high, posterior, 

 nearly opposite the anal, which is similar in form. Tail heterocercal, 

 in the young produced as a filament beyond the caudal fin. Caudal 

 convex. Ventrals nearly midway between pectorals and anal. Pec- 

 toral and ventrals moderate, few-rayed. Vertebrae with ball-and-socket 

 joints {opisthocoelian). Stomach not coecal. Pyloric appendages numer- 

 ous. Spiral valve of intestines rudimentary. Fishes of the fresh waters 

 of North America. Genera 1 or 2; species probably 3 or 4, although 

 more than 40 have been described. These fishes are of much interest 

 to geologists from their relationship to extinct Ganoid types. 



{Lepidosteidce Gunther, viii, 328, 331.) 



* Large teeth of the upper jaw in a. single series (in adult) Lepidosteus, 49. 



** Large teeth of upxier jaw in two series Litholepis, 50. 



49.— IiEPH>®STElIS Lac^pfede. 

 Gar Fikes. 



(Lepisosteus Lac^p^de, Hist. Nat. Poiss. v, 331, 1803 : type Lepisosteiis gavialk Lac. = 

 Eioxosseus L.) 



This genus is characterized by the presence of but one row of largo 

 teeth m each jaw. There are in the upper jaw, first, the outer series of 



