SALMONOID FISHES OF THE GREAT LAKES. 
5 
Thrissomimus: 
b. Species of shore waters, spawning in late autumn, the flesh firm, the skeleton well developed, the 
mouth small, the maxillary not reaching past middle of eye. 
c. Adipose fin very small, usually shorter than eye; body elongate, the caudal peduncle slender, 
its least depth about 3 in head; body slender, the depth 4.33 to 4.66 in length; body anteri- 
orly long, the pectoral not reaching nearly halfway to ventrals; back lustrous bluish in life, 
usually not marked with lengthwise streaks harengus; osmeriformis 
cc. Adipose fin well developed, longer than eye. 
d. Body elongate, the depth 4.33 to 4.5 in length; caudal peduncle slender, its least depth about 
3 in head; body anteriorly long, the pectoral not reaching halfway to ventrals in the 
adult; back dark lustrous blue in life, usually marked with dark lengthwise streaks. 
e. Body subcylindrical, little compressed, its depth about 4.5 in length, its greatest depth 
usually before dorsal sisco; huronius 
ee. Body more robust and more compressed, its depth about 4 in length, the greatest depth 
usually near insertion of dorsal .... ontariensis; lucidus; laurettce; alascanus; pusillus 
dd. Body deep and compressed, the depth 3.33 to about 4 in length; caudal peduncle stout, its 
least depth nearly half head; pectoral reaching more than halfway to ventrals; adipose 
fin larger, longer than eye; back olive-gray, without distinct dark streaks. 
/. Body moderately robust, depth 3.5 to 4 in length; angle at the nape slight, scales rela- 
tively thin and loosely attached artedi; bisselli 
//. Body very robust, depth 3.33 to 3.5 in length, with a strong angle at the nape; scales 
large, regular, and firmly attached; flesh rich, of excellent flavor eriensis 
Cisco: 
bb. Deep-water forms found in 50 fathoms and upward, spawning in midsummer, the flesh soft and 
fat, the skeleton relatively feeble, the mouth relatively large; adipose fin rather large. 
g. Mouth moderate, the maxillary not extending to middle of eye; premaxillary nearly 
horizontal, the upper jaw not truncate; head broad, the width between temples 
rather more than half length of top of head; caudal peduncle stout. 
h. Lower jaw distinctly projecting, its tip somewhat produced upward; head thick; 
eye large; pectoral extending more than halfway to ventrals; depth about 4 in 
length; adipose fin small; fins with little dark. 
i. Head short and slender, 4.66 in length; mouth relatively small; adipose fin rather 
small supernas 
ii. Plead long and thick, 4 to 4.25 in length; mouth large; adipose fin small. 
j. Gillrakers more than 40 prognathus 
jj. Gillrakers fewer than 40 johannce 
hh. Lower jaw included; head long, about 4.5 in length; body moderate, the depth 
about 4.2 in length; caudal peduncle thick; fins all broadly edged with black. 
k. Gillrakers 16 to 19+31 to 35 nigripinnis 
kk. Fins slightly bluish or dusky at tip; gillrakers 14+25 cyanopterus 
gg. Mouth larger, the maxillary extending about to middle of eye; snout long, sub- 
truncate at tip, the premaxillaries more or less vertically placed, lower jaw included; 
body slender, the depth more than 4 times in length; caudal peduncle slender; 
head slender, its breadth at temples half its length above. Color pale, often some 
dark on fins except the ventrals. 
I . Pectoral not reaching halfway to base of ventrals; snout about equal to eye, 
about 4 in head; depth of tail much greater than snout; snout more 
truncate than in next species; scales about 70; color very silvery. . . . hoyi 
II. Pectoral reaching more than halfwaj' to base of ventrals; depth 4.6 to 4.66 
in length; snout less truncate than in L. hoyi, 3 to 3.5 in head, longer 
than eye; depth of tail not equal to snout; scales about 77. Color 
brassy -silvery, with dark points on all fins save ventrals zenithicus 
