12 PEELIMINAKY BEPOET 



BB. Body acaleless, smooth or more or less prickly or warty. 

 D. Cheek (suborbital bone) with a bony stay. 



(Blobs) Cottidae, 74 

 DD. Cheek without a bony stay; dorsal spines 4 to 6. 



(Sticklebacks) Gasterosteidse, 51 

 AAA. Ventral fins absent. 



B. Body long and snake-like; skin covered with elongate, 

 imbedded scales which are arranged at right angles 

 with each other (Eels.) Anguillidae, 41 



Order SELACHOSTOMI. 

 Family POLYODONTIDJ]. The Paddle-fishes. 



Body covered with rather smooth skin; snout prolonged into a 

 long, thin, paddle-shaped projection which is somewhat flexible, 

 and whose upper surface is somewhat reticulated. The mouth is 

 large; there is no tongue present and no barbels on the head. Tail 

 heterocercal. But one genus and one species found in North 

 \ Tn p pi c 9, 



Genus POLYODON Lac6pfede. Paddle-fishes. 

 Polyodon spathula (Walbaum). Paddle-fish. Spoon-bill. Duck-billed Cat. 



A peculiar fish which is at once recognized by the long paddle- 

 shaped snout that reaches about one-third the length of the body; 

 skin on the opercle extending in a long narrow flap; gill mem- 

 branes connected, but free from the isthmus ; teeth numerous but 

 small, disappearing with age; tail heterocercal; gill rakers long 

 and in two rows; length six feet; color bluish or greenish; common 

 in tlhe larger streams of the Mississippi valley. Its food is thought 

 to consist of the small life forms which it roots from the mud 

 with its paddle-shaped bill. Specimens have been taken in Minne- 

 sota from the Minnesota River at Mankato (Cox, 1894), and from 

 the Mississippi Eiver at Minneapolis (Nat. Hist. Surv.). 



Order CHONDROSTEI. 



Family ACIPENSERIDJE. The Sturgeons. 



Body long, spindle-shaped, covered with bony plates, some of 

 which are small and flat, while others are keeled and arranged in 

 rows. The snout is usually somewhat triangular and projects 

 beyond the mouth. Mouth inferior, toothless, extensible for suck- 

 ing up food; four barbels in front of the mouth; gills four in num- 

 ber; tail heterocercal. There are no branchiostegal rays; head 

 covered with bony plates; gill membranes joined to the isthmus; 

 dorsal and anal fins inserted far back; air-bladder large. Two 

 genera and two species occur in Minnesota. 



