PHENACOBIUS SUCKER-MOUTHED MINNOWS 159 



shoulders are also dusted with gold specks; belly silvery; all scales except 

 those of belly sprinkled with minute black specks which become denser at 

 edges of scales; cheeks and opercles silvery with some greenish; pupil brilliant 

 black; iris with a wide inner rim of gold above and silvery below, the outer 

 portion being variegated light or dark green and gold with some silvery below; 

 fins all pale. Head subquadrate in transverse section and flat above, short, 

 3.9 to 4.5 in length; width of head 1.6 to 1.9 in its length; interorbital space 

 flat, 2.7 to 3.3 in head; eye small, 3.6 to 4.8; nose nearly twice length of eye, 

 2.3 to 2.6 in head; mouth very small, wholly inferior and horizontal, the 

 tip of the upper lip on level of chin and breast; maxillary 3.7 to 4.3 in head, 

 not reaching to orbit; lower jaw included; upper jaw provided with a fleshy 

 lip which is continuous on each side with the lower lip, forming laterally a 

 somewhat prominently projecting lobe; the two lobes of the lower lip separated 

 at the middle by a narrow and projecting horny frenum, not separated from 

 the chin by either a groove or a fold; isthmus less than pupil. Teeth 4-4, 

 hooked, one of them occasionally with a narrow grinding surface; intestine 

 about equal to length of head and body; peritoneum plain silvery. Dorsal 

 fin with usually 8 rays, sometimes 7 or 9, always set distinctly in front of 

 ventrals and nearer muzzle than base of caudal; longest dorsal ray 1 to 1.4 

 in head; anal rays 7; pectorals short, reaching little more than half way to 

 ventrals in fully grown specimens; ventrals a little -short of vent in adults. 

 Scales 6, 43-51, 5; rows before dorsal 18 to 22; lateral line complete and 

 little decurved. 



Owing to the range of variation in size of scales in this species, we have 

 found it impossible to separate this and P. scopifer in our collections, and 

 have therefore included the latter species in the synonymy of P. mirabilis. 



This little fish is, in Illinois, upon the eastern border of its 

 range, doubtless extending into Indiana, although not hitherto 

 reported from that state. It is distributed mainly west and 

 south through Iowa to South Dakota and through Missouri to 

 the Sabine and Trinity rivers emptying into the west Gulf. 

 In this state it is of general distribution, occurring in all our 

 river basins, but mainly in the smaller streams. It is most 

 abundant with us in creeks where its frequency coefficient 

 rises to 3.18 and in the smaller rivers 2.19. In the larger 

 rivers its coefficient falls to .32, and in lowland lakes to .05. 

 Although we have taken it in 159 Illinois collections, it has not 

 occurred once in the upland glacial lakes. It is also most abun- 

 dant here in swift streams, particularly in those with a sandy 

 bottom, or in the more rapid and rocky portions of somewhat 

 sluggish creeks. The corresponding coefficients are 1.32 for 

 waters with a rapid flow, and 1.36 for those with a clean bottom. 



Nine of our specimens studied with reference to their food 

 were found to have eaten little but the aquatic larvae of a gnat- 

 like fly (Chironomus) , which is abundant on the bottom and under 



