50 U.S. NATIONAL MUSEUM BULLETIN 282, 



geographic trend in color; some specimens are nearly black, but in 

 preservative most are slate gray. 



A rather obvious trend in the relative lengths of spines and robust- 

 ness of the body exists. Most specimens from the glaciated area of the 

 north central states are plump or fat and have very short spines. 

 Their digestive tracts are literally stuffed with insects. Specimens 

 from Houston, Texas, are slender and emaciated; they have a narrow 

 caudal peduncle and very long spines. Their digestive tracts are 

 empty. Most other long spined individuals from the lower Mississippi 

 Valley and Florida that were examined contain little food. Occasional 

 fat, short spined individuals from the same regions are greatly dis- 

 tended by food, chiefly insects. It is believed that the amount of avail- 

 able food directly controls the relative growth of the framework parts. 

 Where little food is available, the hard skeletal parts grow at the ex- 

 pense of the soft tissues; where much food is available, all parts grow 

 uniformly. 



No quantitative study of the amount of food utilized is available, 

 but comparative growth rates of parts on different quantities of food 

 should be determined. As an indication of the variation, the following 

 stepped proportions are given (number, range, and mean in sequence) 

 from: (a) New Jersey, (b) Michigan, (c) Missouri, (d) Texas, and 

 (e) Florida. 



Least peduncle depth in predorsal length: (a) 15 (2.1-3.0) 2.6; (b) 15 

 (2.3-2.7) 2.5; (c) 15 (2.4-3.0) 2.7; (d) 20 (2.5-3.0) 2.7; (e) 21 (2.6-3.1) 

 2.9. 



Pectoral spine length in predorsal length: (a) 24 (2.4-3.7) 3.0; (b) 26 

 (2.4-3.3) 2.9; (c) 30 (1.9-2.6) 2.3; (d) 39 (1.6-2.5) 2.1; (e) 41 (2.0-2.8) 

 2.3. 



Pectoral spine length in peduncle depth: (a) 24 (0.8-1.7) 1.2; (b) 26 

 (0.8-1.5) 1.2; (c) 30 (0.7-1.0) 0.8; (d) 39 (0.5-0.9) 0.7; (e) 40 (0.6-1.0) 

 0.8. 



Dorsal spine length in predorsal length: (a) 14 (3.2-4.5) 3.9; (b) 15 

 (2.9-4.5) 3.5; (c) 14 (2.2-3.4) 2.8; (d) 20 (2.0-3.0) 2.6; (e) 20 (2.3-3.5) 

 2.7. 



Standard lengths (mm.): (a) 15 (24-60) 39.4; (b) 15 (32-60) 44.5; 

 (c) 15 (33-47) 38.4; (d) 20 (38-50) 44.1; (e) 20 (35-60) 42.5. 



Distribution. — Noturus gyrinus (map 1) is found from Saskatch- 

 ewan, Manitoba, the Dakotas, Nebraska, Kansas, Oklahoma, and 

 Texas eastward to the Atlantic coast. New York, and the Saint 

 Lawrence River system. It has been introduced elsewhere. It avoids 

 the uplands of the Ouachita Mountains of Arkansas, the Ozark 

 Plateau of Arkansas and Missouri, the Appalachian Highlands, and 

 the Piedmont Plateau. On the Atlantic coast it occurs chiefly below 

 the Fall Line (approximately the line indicated on map 1) and ranges 



