GWYNIAD. 
905 
A: Shallow-snouted , as a rule with dense 
gill-rakers: depth of the tip of the 
snout at the rostral protuberances (a 3 a 4 , 
see fig. 228) less than 15 % of the 
length of the head reduced (ad, see fig.); 
gill-rakers on the first branchial arch 
as a rule more than 30. 
a: Length of the maxillaries more 
than 30 % of that of the head. Gill- 
rakers on the first branchial arch 
more than 50. (A Siberian form) Coregonns muksun. 
b: Length of the maxillaries less than 
30 % of that of the head. Gill- 
rakers on tire first branchial arch 
less than 50.- Cor eg onus Wartmanni. 
a: Depth of the tip of the snout 
less than 61 % of its breadth 
(cija 2 , see fig.). 
aa: Least depth of the peduncle 
of the tail less than 36 % 
of the length of the head 
— Cor. bolmensis. 
bb : Least depth of the peduncle 
of the tail more than 36 % 
of the length of the head. 
aa: Gill-rakers on the first 
branchial arch less than 
40 — Cor. Nilssonii. 
(3(3 : Gill-rakers on the first 
branchial arch more 
than 40 — Cor. as pi us. 
(3: Depth of the tip of the snout 
more than 61 % of its breadth 
— Cor. Wartmanni. 
B : Deep-snouted , as a rule with scattered 
gill-rakers : depth of the snout at the 
rostral protuberances more than 15 % 
of the length of the head reduced; 
gill-rakers on the first branchial arch 
as a rule less than 30. 
a: Length of the maxillaries more 
than 30 % of that of the head Coregonns maraena. 
a: Length of the maxillaries less 
than 76 % of that of the lower 
jaw — Cor. maxi liar is. 
(3: Length of the maxillaries more 
than 80 % of that of the lower 
jaw — Cor. oxyrhynchus. 
l>: Length of the maxillaries less than 
30 % of that of the head. 
a: Length of the lower jaw greater 
than the least depth of the tail Coregonus lavaretus. 
aa : Length of the head more 
than 18 % of that- of the 
body. 
aa: Vertical diameter of 
the eyes more than 24 
% of the length of the 
head reduced — Cor. 
lavaretus. 
(3(3: Vertical diameter of 
the eyes less than 24 
% of the length of the 
head reduced — Cor. 
m i crops. 
bb: Length of the head less 
than 18 % of that of the body 
— Cor. microeephalus. 
Fig. 228. Outline drawing of a Gwyniad ( Coregonus Nilssonii ), showing how the measurements in the table of averages are taken. 
Line ab = length of the body. 
ac = ,, ,, ,, head. 
ad = ,, ,, ,, ,, reduced. 
a,a 2 = breadth of the snout. 
H a \ = depth „ ,, „ 
ag = length „ „ 
gh = longitudinal diameter of the eyes. 
ef = vertical ,, ,, ,, ,, 
ai = length of the maxillaries. 
mn ----- breadth ,, ,, ,, 
Tel — length of the lower jaw. 
op = length of the suboperculum. 
ag = distance between the dorsal fin and the 
tip of the snout. 
qr = base of the dorsal fin. 
st = height ,, „ „ „ 
uv = length of the pectoral fins. 
uiv = preabdoininal length. 
aiv = distance between the ventral fins and the 
tip of the snout. 
wee = length of the ventral fins. 
wy = postabdominal length. 
ay = distance between the anal fin and the tip 
of the snout. 
yz = base of the anal fin. 
a(3 = height ,, ,, ,, „ 
yd = dorsal margin of the peduncle of the tail. 
kxk = length ,, „ ,, ,, ,, ,. 
zE = ventral margin ,, ,, ,, ,, ,, ,, 
Crj = least depth „ ,, „ ,, ,, 
d~b = length of the middle caudal rays. 
I'A = ,, ,, ,, longest rays in the upper 
caudal lobe. 
