PHENACOBIUS SUCKER-MOUTHED MINNOWS 159 



caudal spot and a narrow vertebral streak, golden in life, when the 

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

 except those of belly sprinkled with minute black specks which be- 

 come 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 subquad- 

 rate 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 hornv fre- 

 num, 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 nar- 

 row 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. scopijer 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 



ts frequency coefficient rises to 3 . 1 8 — 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 bot- 

 tom, 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 stones. 



