90 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — IV. 
forming- most of the margin of the npi^er jaw; the maxillary transversely 
divided into several pieces. Lower jaw composed of as many pieces as 
in reptiles. Coronoid present. Both jaws with an outer 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 5u 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 i^eculiar. 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. Xo spiracles. Gills four, a slit be- 
hind the fourth. Branchiostegals 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, 
nearl}^ opposite the anal, wliich 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. Yertebrse with ball-and-socket 
joints {opisthocoelian). Stomach not coecal. Pyloric appendages numer- 
ous. Spiral valve of intestines rudimentary. Fishes of the fresh waters 
of Xorth 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. 
{Lvpidostcida; Giiutlier, viii, 328, 331.) 
* Large teetli of the upper jaw in a siugle series (in adult) Lepidosteus, 49. 
** Large teeth of upper jaw in two series Litholepis, 50. 
49.— L.EPBI>®STEUS Lacdpede. 
Gar Pikes. 
(Z^nsosfeas Lac^pede, Hist. Nat. Poiss. v, 331, 1803: type Lepisosteus gavialis hac. = 
Eaox osseus L.) 
This genus is characterized by the presence of but one row of largo 
teeth in each jaw. There are in the upper jaw, first, the outer series of 
