$4 COXTKIBT'TIOXS TO NORTH AMERICAN ICHTHYOLOGY - IV. 



I.. ."-; feet. Mississippi Valley and rivers of the Southern States; gen- 

 erally abundant. 



(N.//;,i/.t Kixilluiln Wall):ui!ii, Artrdi Pise. 1792, 522: "Polijodon fcuillc" Lac^i^dc, 

 Ili-r. N;ii. I'..;--, i. I"'.' : I', folium SrlmHder ed. Bloch, Syst. Ichth. 457 : Sp<tlulari<i 

 tint, i HI:I\V, Ccii. Z<>nl. l-oi. v, '.'i'rJ: I'ltiiirostra edcntula (adult) Lo Sueur, Journ. 

 . N:it. ScL I'liiln. .".'7 : / '../y/i'Hwi; anther, 34G.) 



ORDER II.-GLANIOSTOMI. 



(The Sturgeons.) 



A priecoracoid arch. No symplectic bone. Maxillary present. Xo 

 snboperculam or preoperculuml Interoperculum present. Mesoptery- 

 gium distinct. Interclavicles present. Basihyals and superior cerato- 

 hyal not ossified. Branchihyals osseous. This group is composed of the 

 le family Acipenseridce. (flavcs, a cat-fish, Silurus ; aru;>.aj mouth.) 



FAMILY XXVI. ACIPENSERIDCE. 



(The Sturgeons.) 



r.ody elongate, subcylindrical, armed with five rows of bony bucklers, 

 cadi with a median carina which terminates in a spine. A median dor- 

 sal series, and a lateral and abdominal series on each side, the abdomi- 

 nal series sometimes deciduous. Between these the skin is ron.uli, with 

 small irregular plates. Snout produced, depressed, conical or subsput- 

 nlate. .Mouth small, inierior, protractile, with thiekeiied lips. No 

 leeth. Four barbels in a transverse series on the lower side of the 

 snout in front of the mouth. Eyes small; nostrils large, double, in front 

 of eye. Gills I. A n accessory opercular gill. Gill membranes united 

 to the isthmus. No branehiostcgals. Maxillary bone distinct from the 

 pi- -maxillary. Head covered with bony plates united by sutures. Fin- 

 nix s slender, all articulated. Vertical fins with fulcra. Pectorals 

 placed low. Ventrals many-rayed, behind middle of body. Dorsal 

 plaeed ]Hierioily. A nal somewhat behind it, similar. Tail heterocer- 

 cal. the lower caudal lobe developed. Air-bladder large, simple, con- 

 nected \\ith tlieii-sophagns. I'seudobranchia' small orobsolete. Stom- 

 ach \\ithoiit blind sac. KYctuin \\ith a spiral valve. Pancreas divided 

 into pylorie appendage-. 



Large tabes f the Beas and fresh waters of northern regions. "Most 

 of the species are ini-ratory, like the salmon, which are found hi the 

 same \\ uters. Genera i', species about 20, although more than five 

 times that number have been described. The American species especi- 



