POLYODONTIDJE. CXIV. 311 



(August Dume'ril). Perhaps in no group has the making 

 of nominal species been carried to a greater extent than 

 in this. 



* Rows of bony bucklers distinct throughout ; spiracles present ; 



snout rather narrow, sub-conical. . . ACIPENSER, 1. 



** Rows of bony bucklers confluent behind, entirely surrounding 

 the depressed tail ; no spiracles ; snout flattened, rather broad, 

 shovel -shaped SCAPHIRHYNCHUS, 2. 



/. ACIPENSER, Linnaeus. STURGEONS. 



* Marine species ascending rivers ; lateral shields 22 to 32. 



1. A. stur/'o, L. COMMON SEA STURGEON. SHARP - 

 NOSED STURGEON. Snout pointed, half the length of 

 head; dorsal shields 11 to 13; lateral shields 26 to 31; 

 D. 37 to 44 rays. Atlantic Ocean S. to Africa and West 

 Indies. (A. oxyrhynchus^ Mit., the American form.) 



2. A. brevirosiris, LeSueur. BLUNT-NOSED STURGEON. 

 Snout blunt, one-quarter length of head; dorsal shields 

 8 to 10; lateral shields 22 to 28; abdominal 8 to 10; D. 

 30 rays; skin with minute scattered prickles and stellate 

 ossifications. Cape Cod to Fla. 



** Species of fresh water ; lateral shields 33 to 38. 



3. A. macu/osuSf LeSueur. ROCK STURGEON. BONY 

 STURGEON. Snout pointed, nearly as long as rest of 

 head; head 3^ in length of body; bony shields large, 

 close together, 13 to 16 in front of dorsal, 33 to 38 on 

 sides, 9 or 10 on abdomen, all of them rough and strongly 

 radiated, with more or less hooked or incurved tips; skin 

 rough; D. 37 to 45. Great Lakes, Ohio B. and north- 

 ward. (Possibly the young of the next ?) 



4. A. rubicundus, LeSueur. RED STURGEON. LAKE 

 STURGEON. Head 4-J in length; eye 10 in head, nearly 

 midway; dorsal scutes 16 (to base of D), relatively small 



