90 CONTKII'.ITIOXS TO NORTH AMERICAN ICI1TUYOLOGY IV. 



forming iim>i of tin- margin of the upper jaw; the maxillary transversely 

 divided into several pieces. Lower jaw composed of as many pieces as 

 in reptiles. Coi^noid present. IJoth jaws with an outer scries of small 

 ;h, fellowe.l by one (or two) series of large teeth, besides which on 

 the jaws, vomer, and palatinesare series of small, closc-.set, rasp-like teeth. 

 Ton-lie toothless. Large teeth of the jaws conical in form, pointed and 

 stiiate. piaeed at right angles to the jaw. These large teeth rest, accord- 

 in- to Agassi/, in a rather deep furrow, protected oil 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. Xostrils near 

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

 operde. PseudobranchiaB 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 

 esophagus. Fins with fulcra. Dorsal tin short, rather high, posterior, 

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

 in the young produced as a lilament beyond the caudal lin. Caudal 

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

 toral and ventrals moderate, feu -rayed. Vertebra 1 with ball-and-socket 

 joints (njiixthiHwlian). IS tomach not coical. Pyloric appendages numer- 

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

 of North America. Genera 1 or 2; species probably '.'> or 1. although 

 more than 10 have, been described. These tishes are of much interest 

 to .geologists from their relationship to extinct Ganoid types. 

 " liiiiiilirr, \iii. 328, :::n.) 



;<-Hli of tin- npjH-r j:i\v iii a Mii^lr si-rirs (in adult) .......... LKIII><>STI is, !'.>. 



Mi i.f n|i]n>r j:i\\ in i \\, Ncii.-s ............................ Li ..... i. ri MS, 50. 



lf>.-L,EPIDOSTEUS 



Oar Pikes. 



''"' |"'l"', lli-t. Nat. 1'niss. v, 331, 1803: typo /.< i>i<>*tni* iKirialin Lac. = 



'' ) 



This genus is chai acteri/.ed by the presence of but one row of largo 

 li in each j iw. There are in the upper jaw, first, the outer series of 



