LABIDESTHES — BROOK SILVERSIDES 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 SILVERSIDES) 



Body elongate, more or less compressed; belly rounded before ven- 

 trals; 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) 



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



J. & G., 406; M. v., 100; J. & E., I, 805; X., 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 ver}^ distinct lateral silvery band, scarcely broader than 

 pupil, bounded above by a dark line; back dotted 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 1 1 ; 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 Kaskaskia, the 

 Big Muddy, the Saline, and the waters of extreme southern Illinois. 



