LABIDESTHES — BROOK SILVEBSIDES 227 



"Carnivorous fishes, mostly of small size, living in great 

 schools near the shore in temperate and tropical seas; a few 

 species in fresh water." A single genus and species found in 

 Illinois waters. The presence in all the species of a silvery band 

 along the side, often underlaid by black pigment, gives the 

 common name to the family. 



Genus LABIDESTHES Cope 



BROOK SILVEBSIDES 



Body elongate, more or less compressed; belly rounded before ventrals; 

 head oblong, compressed; mouth small, the cleft curved, oblique, the jaws 

 being prolonged into a short depressed beak; premaxillaries freely protractile, 

 broad behind; lower jaw longer than upper; no teeth on vomer or palatines; 

 both dorsals short; scales with entire edges. Eastern North America to 

 Texas; confined to fresh waters; a single species known. 



LABIDESTHES SICCULUS (Cope) 



BROOK SILVERSIDE 



(Ph. p. 220; Map LXVIII) 



Cope, 1865, Proc. Ac. Nat. Sci. Phila., 81 (Chirostoma). 



J. & G., 406; M. V., 100; J. & E., I, 805; N"., 42; J., 51; F., 70; F. F., I. 6, 69; L., 22. 



Length 3 inches: body quite slender and elongate and considerably 

 compressed; depth 6 to 8; greatest width about % in greatest depth; depth 

 of caudal peduncle 2.3 to 3 in its length. 'Color pale olive-green, translucent; 

 a very distinct lateral silvery band, scarcely broader than pupil, bounded 

 above by a dark line; back clotted with black' (J. & E., slightly emended); 

 dorsal of males tipped with black. Head long and pointed, flattened, and 

 broader above than below, 4.1 to 4.6; width of head 2.1 to 2.5; interorbital 

 space 3.5 to 4; eye 3.5 to 4; nose long and slender, the jaws prolonged into a 

 short depressed beak, whose length is nearly twice the eye; mouth large, 

 maxillary to front of orbit, cleft 2.2 to 2.6; jaws equal, edge of upper jaw 

 strongly concave. Dorsal IV— I, 9 to 11; first dorsal inserted slightly behind 

 front of anal; caudal forked; anal I, 21 to 24; ventrals abdominal, much 

 nearer front of anal than throat; pectorals nearly to ventrals, 1.3 to 1.6 in 

 head. Scales cycloid, 15-16, 75-79; lateral line represented by a few isolated 

 pores (as a rule only on caudal peduncle) ; cheeks and opercles scaled. 



This delicate and exquisite little fish, slender as a pike, semi- 

 translucent, and decorated with lateral stripes of brilliant silver, 

 is distributed through the northern, central, and eastern parts 

 of the state, but is wanting in all our collections from the Kas- 

 kaskia, the Big Muddy, the Saline, and the waters of extreme 

 southern Illinois. It evidentlv avoids the lower Illinoisan 



