nn. Fine without spines: scales cycloid: many pyloric caeca Salmonid^. 



dd. Dorsal fin preceded by fourormore free spines Gastbrosteid^. 



ddd. Dorsal fin preceded by a flnlet of four slender spines Atherinid^. 



2. Ventral fins wholly wanting, 



a. Body much elongated; dorsal, anal, and caudal fins continuous around body. 



Anodillid^. 



aa. Body not elongate; fins separate; eyes imperfect Amblyopsid^. 



3. Ventrals thoracic or jugular, the number of rays not I, 6, but usually 1,7; dor- 



sal with three or four spines: scales strongly ctenoid Aphrkdoderid^e. 



4. Ventral fins thoracic or subjugular; the number of rays definitely I, 6; dorsal 



with spiny and soft rays ; slit behind fourth gill large: body scaled. 



a. Lateral line never extending on rays of caudal fin; often incomplete or wanting. 



b. Pseudobranchia undeveloped, 



c. Anal spines 3 to 10. 



d. Dorsal spines 4; lateral line wanting ELA8soinD.ai. 



dd. Dorsal spines 6 to 12; lateral line well developed Ckntrarohid^. 



cc. Anal spines 1 or 2; small fishes under eight inches long Pkroid^. 



bb. Pseudobranchia developed, 



e. Anal spines 2 (or 1); pseudobranchia small; cylindrical fishes Pebcid^. 



ee. Anal spines 3; compressed fishes Serbanid^. 



aa. Lateral line extending to tip ef middle ray of caudal fin SoiAENiDiB, 



5. Ventral fins I, 3 or I, 4; slit behind the fourth gill small or wanting: scaleless. 



COTTID^. 



A A. Chin with a median barbel; body elongate; dorsal and anal fins elongate: scales 

 embedded Gadid^s. 



Family Petromyzonid^ (The Lampreys). 

 Ichthyomyzon concolor (Kirtland). — Silvery Lamprey. (5) 



Taken five times from the Illinois River and once from the Wabash river at Mt. Carmel. 

 Ichthyomyzon castaneus Girard. (4) 



One example of this species was obtained at Pekin, 111., April 16, 1880. 



Lampetra wilderi Gage. — Brook Lamprey; Small Black Lamprey. (3) 



We have records of the occurrence of this species at Cairo, Pekin, and Peoria: also found 

 several times by Dr. Jordan in small streams of Illinois. 



Family Polyodontid^ (The Paddlepishes). 



Polyodon spathula {Walh&nm). — Spoonbill Cat; Spoonbill; Paddlefish. 



This fish feeds upon the minute animal and plant life of the water. Its snout probably 

 serves as a delicate sense organ. 



Formerly abundant in all large streams, but now apparently decreasing greatly in num- 

 bers. Now fciund only sparingly in the larger streams tributary to the Missiasippi and in 

 adjacent ponds and lakes. 



Family Acipenserid^ (The Sturgeons). 



Acipenser ruhicundus Le Sueur. — Lake Sturgeon; Rock Sturgeon; Red 

 Sturgeon. 



The red sturgeon is usually a rather sluggish fish. The color changes with age. the 

 young being drab and the adults green or red. 



Formerly abundant in rivers and in Lake Michigan, but rarely taken now. Occurs five 

 times in our collections, being listed from tributaries of the Mississippi and from the Great 

 Lakes. 



