34 PISCES : — GLANIOSTOMI. — VIII. 
branchiostezals; head covered by bony plates joined by sutures; 
gill membranes joined to isthmus; vertical fins with fulcra; dorsal 
and anal posterior; tail heterocercal; air-bladder large, simple; 
stomach not cecal, with pyloric appendages; rectum with spiral 
valve. Seas and rivers of northern regions; feeding on small 
animals and plants sucked in through the tube-like mouth. Genera 
2, species about 20. 
The sturgeons change considerably with age. The snout be- 
comes shorter and blunter, the shields smoother, and some of the 
shields often fall off or are absorbed in old age. 
uw. Spiracles obsolete; snout broad, shovel-shaped, depressed above; rows of 
bony shields coalescent behind the dorsal, so that the depressed tail is 
completely mailed; gill rakers small, fan-shaped, ending in 3 or 4 points. 
ScaPHIRHYNCHUuS, 380. 
aa. Spiracles present; snout sub-conic; rows of bony shields nowhere con- 
fluent, the tail not depressed nor mailed; gill rakers lanceolate. 
ACIPENSER, 31. 
30. SCAPHIRHYNCHUS Heckel. (Scaphirhynchops Gill.) 
(cxagn, spade; puyxos, snout.) 
40. S. platyrhynchus (Rafinesque). SHOVEL-NosED StTuR- 
Gron. Wuite SrurGreon. Body elongate, tapering into the 
slender depressed tail, which extends in the young beyond C. as a 
slender filament; shields sharply keeled; dorsal shields 15 to 18; 
lateral, 41 to 46; ventral, 11 to 13. L. 5 fcet. Miss. Valley, etc., 
common. (mAartus, flat; poyxos, snout.) 
31. ACIPENSER (Artedi) Linneus. (Lat., sturgeon.) 
a. Plates between vent and A. large, in one or two rows. 
6. Space between dorsal and lateral shields with stellate plates of moder- 
ate size in 5 to 10 series: last dorsal shield of moderate size, more 
than half length of one before it. 
41. A. sturio L. Common Sturceon. First dorsal fulcrum 
somewhat enlarged, its surface rough; dorsal shields 9 to 11; 
lateral shields 26 to 31; ventral, 9 or 10; 2 rows of 2 shields each, 
with one median shield between vent and anal. D. 40, A. 26. 
L. 8 to12 feet, N. Atlantic, ascending rivers; commonest N., S. 
to S. C. (A. ozyrhynchus Mitchill, the American form; said to 
have usually fewer lateral shields.) (Eu.) (Lat., sturgeon.) 
6b. Space between dorsal and lateral shields with minute plates in very 
many series. 
c. Last dorsal shield of moderate size, more than half length of next 
the last ; dorsal shields 15 or 16. 
“42. A. rubicundus Le Sueur. Laxe Sturcron. Rock Stur- 
q@ron. First dorsal fulerum slightly enlarged; dorsal shields 15; 
lateral 38, ventral 10; 3 shields in a single row between anal fin 
