CAMPOSTOMA STONE-ROLLERS 111 



times diameter of orbit. Teeth 4-4 or 1, 4-4, 0, with oblique grinding 

 surface without terminal hooks, or with only a slight one on one or two 

 teeth; intestine 5 to 9.5 times length of head and body; peritoneum black. 

 Dorsal fin with 8 rays, set slightly behind ventrals and nearly midway 

 between muzzle and base of caudal; longest dorsal ray 1.2 to 1.6 in head; 

 anal ravs 7 ; pectorals about § to ventrals, 1.2 to 1.4 in head, ventrals fall- 

 ing quite short of vent in males, reaching or almost reaching it in females. 

 Scales rather small, 6-8, 46-53, 6-8, more or less crowded forward, the 

 crowding scarcelv noticeable in females but ver\' evident and often con- 

 spicuous in old males; scales on breast ver\' small, about 15 transverse 

 series between pectorals ; scales before dorsal 1 5 to 2 6 ; lateral line complete. 



This is a species of wide distribution occurring in the Great Lake 

 region, along the south Atlantic slope to the Gulf, and in the valley 

 of the Mississippi from Wyoming to Indiana, Ohio, and Texas. 



It is a fish of the creeks and the smaller rivers, its ratios of pref- 

 erence, according to our collections, being 3| for the former and 

 2\ for the latter. It has been taken only occasionally by us from 

 rivers of a large size, and but rarely from lakes and ponds. Indeed, 

 the notable preference of the species for rocky or sandy streams as 

 shown by its frequency coefficient of 3.26, and for swift water over 

 still water (coefficients respectively, 1.70 and .59) would tend to 

 exclude it from stagnant or muddy waters of any description. In 

 accordance with these preferences, it has not once occurred in our 

 collections from the streams of the lower Illinoisan glaciation, none 

 of our 166 Illinois localities for this species falling within that dis- 

 trict. Nine of them are from the hill region of extreme southern 

 Illinois, and one is from the Wabash in Wabash county, but the 

 southernmost points for the remaining 156 localities are in Mont- 

 gomery county in the western part of the state, and in Coles county 

 in the eastern part. 



This species is distinguished from all our other minnows by the 

 great length of the intestine, which is wound spirally about the air- 

 bladder. There are about twenty gill-rakers to each gill, but they 

 are so short as to constitute a very inefficient straining apparatus. 

 The pharyngeal teeth have well-developed grinding surfaces, and 

 are practically without terminal hook. Intestines of specimens 

 examined with reference to the food of the species were invariably 

 found filled from end to end with a slime-like matter consisting 

 almost wholly of fine mud from which, with proper treatment, frag- 

 ments of organic matter could be readily separated. This was 

 nearly all of vegetable origin, chiefly filamentous algae, with diatoms, 

 and minute fragments of various kinds of plant tissue. Sometimes 

 the intestine was filled with almost pure mud. 



