102 Bulletin 47, United States National Museum. 



rhombic plates on the sides of the tail. Ventrals near the middle of the 

 body; dorsal well behind them ; anal mostly behind the dorsal, and some- 

 what larger; these fins somewhat falcate. Fin rays slender. Spiracle 

 with a minute barbel. Isthmus papillose in the young. Spatula broad, 

 2^ to 4 times in length, proportionately longer in young. Head, with 

 opercular flap, more than \ length; head, without spatula flap, about 5. 

 Color pale olivaceous. D. 50 to 60 ; A. 50 to 65 ; V. 45. L. 5 to 6 feet. 

 Mississippi Valley and rivers of the southern States ; generally abundant 

 in the larger streams ; also known from Lake Erie. A singular fish of 

 rather sluggish habits, the flesh coarse, resembling that of the larger cat- 

 fishes, but inferior in quality, (spathula, spatula.) 



Squalus spathula, WALBAUM, Artedi Pise., 522, 1792, after Spathula of Rozier, Jour. Phys., 1774, 

 384, pi. 2. 



"Polyodon /euitfe," LAC^PEDE, Hist. Nat. Poiss., i, 402, 1798, locality unknown. 



Polyodon folium, BLOCH & SCHNEIDER, Syst. Ichth., 457, 1801, after Lacepede. 



Spaiularia reticulata, SHAW, Gen. Zool., v, 362, 1804, after Lac6pede. 



Plalirostra edentula (adult), LE SUETIR, Jour. Ac. Nat. Sci. Phila., i, 1817, 227, Ohio River. 



Polyodon folium, GIJNTHER, Cat., vnr, 346, 1870. 



Polyodon spathula, JORDAN & GILBERT, Synopsis, 83, 1883. 



Acipenser lagenarius, RAFINESQTJE, Ich.Oh.,86,1820, Ohio River. 



Procerus maculatus, St. Genevieve, Missouri, and Proceros vittatus, Lake Ontario, RAFIN- 

 ESQTJE, Ich. Oh., 8fi, 87, 1820. 



Planirostra spatula, OWEN, Osteol. Cat., I, 83, 1853. 



Order J. CHONDROSTEI. 

 (THE STURGEONS.) 



Notochord persistent, the cartilaginous vertebrae imperfectly developed. 

 A mesocoracoid. No symplectic bone. Maxillary present. No eub- 

 operculum or preoperculum. Interoperculum present. Mesopterygium 

 distinct. Interclavicles present. Basihyals and superior ceratohyal not 

 ossified. Branchihyals osseous. This group is composed of the single 

 family ACIPENSERID/E. (xovdpoc, cartilage; bortov, bone.) 



Family XXXI. ACIPENSERID^E. 



(THE STURGEONS.) 



Body elongate, subcylindrical, armed with 5 rows of bony bucklers, 

 each with a median carina which terminates in a spine, which sometimes 

 becomes obsolete with age ; a median dorsal series, and a lateral and 

 abdominal series on each side, the abdominal series sometimes decidu- 

 ous; between these the skin is rough with small irregular plates. Head 

 covered with bony plates joined by sutures; snout produced, depressed, 

 conical, or subspatulate. Mouth small, inferior, protractile, with thick- 

 ened lips. No teeth. 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 4; an accessory opercular gill; gill membranes united 

 to the isthmus ; no branchiostegals. Maxillary distinct from the premax- 

 illary. Head covered with bony plates united by sutures. Fin rays 

 slender, all articulated ; vertical fins with fulcra. Pectorals placed low ; 

 ventrals many-rayed, behind middle of body; dorsal placed posteriorly ; 



