(;\\VM.\i>. 



905 



; Sludlow-snotiteil, i\s a rule with dense 

 qill-rakers: depth of the tip of the 

 snout at the rostral protubcranccs(a3a4, 

 see fig. 228) less than 15 % of the 

 length of the head reduced (a(/, see fig.); 

 o-ill-rakers on the first luanchial arch 

 (IS a rule more than SO. 

 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) Coregomis iniikann. 

 b: Length of the maxillaries less than 

 30 ". of tliJit of the head. Gill- 

 rakers on tlie first branchial arcli 



less than 50 _ (Jorei/oniis W'urtmanni. 



a: Depth of the tip of the snout 

 loss than ()1 % of its breadth 

 (((|0.,, see fig.). 



act: 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 3(5 ". 



of the length of the head. 



««; Gill-rakers on the first 



branchial arch less than 



40 — Cor. Xilssonii. 



;S/J.- Gill-rakers on the first 



brauehinl arch more 



than 40 — Cor. aspius. 



/•;.■ Depth of the tip of the snout 



more than (11 % oi' its breadth 



— Cor. AVartmanui. 



/i: l)eeji-sitoHteJ. 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 ma.xillaries more 



than 30 % of that ol' the head Coreeiotins inaraiiia. 



a: Length of the maxillaries less 

 than 7() % of that of the lower 

 jaw — Cor. maxillaris. 

 li: Length of the maxillaries more 

 than 80 °i of that of the lower 

 j aw — Cor. o X V r h y n c h u s . 

 li: Length of the maxillaries less than 

 30 •• of that of the head. 

 a: Length of the lower jaw greatei' 



than the least depth of the tail (Joregoims lavaretus. 

 aa: Length of the head more 

 than 18 % of that of the 

 body. . S, 



an: \'ertieal diameter of 

 the eyes more than 24 

 % of the length of the 

 head reduced — Cor. 

 lavaretus. 

 iiji: Vertical diameter of 

 the eyes less than 24 

 % of the length of the 

 head reduced — Cor. 

 mi crops. 

 bb: Length of the head less 

 than 18 % of that of the body 

 — Cor. microcephalus. 



Fig. 22.'*. Outline drawing- of a Gwyuiad (Coregoiuis Xilssonii), sliowing how the iiieasiiremeuts in flie (able of averages arc taken. 



Line ab = length of the body. 



«c =: .. ,, ,, head. 



ad = ., .. ,. ,, reduced 



a^a., = breadtli of the snout. 



V4 = '''^Ptli , 



ag = length ,. ,, ,, 



op = length of the suboperculum. , ai/ = distance between the annl fin and tlu- tip 



aq = distance between the dorsal fin and the I of the snout. 



tip of the snoui. 

 Yr = ba.'^e of the dorsal fin. 

 St = height .. „ 

 uv = length of the pectoral fins. 

 gti = longitudinal diameter of the eyes, j uw = preabdoiniual length. 

 ef = vertical ,. ,, .. ,, me = distance between the ventral tins and the 



ai = length of tlie maxillaries. 

 mil --- breadth ,, ,, ,, 



kl = length of the lower jaw. 



tip of the snout. 

 IV.T = length of the ventral fins 

 7VJ/ = postabdoininal length. 



yz = base of the anal fin. 

 a/S = height ,, ,, ., ,. 

 yd = dorsal margin of the ]iedimcle of the tail. 



l» = length 



zE = ventral margin ,, ., .. 



C?] = least depth ,. ,. .. .. ,, 



^■4 = length of the middle caudal rays. 

 /■/. = ,, ,, ,, longest rays in the upper 

 caudal lobe. 



