SCAPHIRHYNCHUS SHOVEL-NOSED STURGEONS 27 



SCAPHIRHYNCHUS PLATORHYNCHUS (EAFINESQUE) 



SHOVEL-NOSED STURGEON 



(PL, P. 26) 



Rafinesque, '20, Ichth. Oh., 80 (Acipenser). 

 G., VIII, 345 (cataphractus); J. & G., 88 (Scaphirhynchops) ; M. V., 34; J. & E., 



I, 107; N"., 51 (Scaphirhynchops); J., 69 (Scaphirhynchops); F., 85 (Schaphirhyn- 



chops) ; L., 8. 



Body comparatively elongate; depth 6.7 to 11.7 in length; distance 

 from gill-opening; to front of dorsal fin 2.1 to 2.2 in length without caudal; 

 length 2 to 3 ft.* Color pale olive, darker above, where the color is often 

 a yellowish brown; belly whitish. Head 3.5 to 3.8 in length of head and 

 body; rostrum comparatively short and wide, its greatest width 1.3 to 1.6 

 in its length; interorbital space 3.3 to 3.7 in head; eye 5.3 to 8.3 (usually 

 less than 7) in interorbital space; mouth wide, 1.6 to 1.9 in greatest width 

 of rostrum ; labial papilla; well developed ; barbels flattened, the anterior edge 

 furnished with one. and the posterior edge with two rows of branched fringe- 

 like pectinations; inner barbels 1.1 to 1.4 in length of outer; gill-membranes 

 meeting at the isthmus in a rather shallow and usually quite obtuse angle, 

 the membranes foreshortened, as a rule falling short of the notch in the 

 pectoral shields; gill-rakers 12+5, 2- to 5-pointed on the lower half of arch, 

 the upper surface of which is a narrow edge, scarcely separating the outer 

 and inner rows of rakers. Dorsal rays 28 or 29, length of base of fin 12 to 

 14.3 in length of head and body; anal rays 17 or 18, ventral 21 or 22, pectoral 

 43 or 44; caudal filament very much elongated in younger specimens. Dorsal 

 scutes 17 or 18, lateral 42 to 47 (usually 42-44), ventral 11 to 13; spines of 

 dorsal and lateral scutes falling considerably short of their posterior edge; 

 area on body between dorsal and lateral and between lateral and ventral 

 series of scutes entirely covered with small, irregularly shaped scale-like 

 plates; belly and breast completely armored, the plates subrhombic in form, 

 becoming much smaller forward. 



This fish is fairly common in the Mississippi, Ohio, and Mis- 

 souri rivers, and in the other larger streams of the Mississippi 

 Valley, being more abundant southward. Little is known of 

 its habits. It spawns between April and June, probably ascend- 

 ing smaller streams for that purpose. The stomachs of two 

 specimens studied by us were found to contain considerable 

 quantities of a greenish gnat larva (Ceratopogori) , a small num- 

 ber of nymphs of May-flies (Hexagenia), a single dragon-fly 

 nymph (Libellula pulchella), which occurs on bottom mud in 

 comparatively shallow water, and a few caddis-fly larvae (Phry- 

 ganeidce) . 



* Of 41 males and 21 females recently examined by Dr. Evermann (Rep. U. S. Fish Comm., 

 1901, pp. 285-286) the average length and weight for females was 25.4 inches and 3.24 Ib, the 

 largest female being but 29.5 inches long and weighing 4.75 Ib, while males averaged 21.7 

 inches and 1.89 Ib, the longest being 27 inches. These measurements are considerably under 

 those usually assigned in the literature, and it seems probable that the species rarely reaches 

 a length greater than 3 feet. 



