SALM(J ( )BTUSIR( )STRIS. 



287 



Fig. 148. — VOMER 



OF SALMO OKTU- 

 SIKOSTKIS. 



The height of the body is always more than the length of the head, which 

 is one-fifth of the total length of the fish. The head is shortei', both abso- 

 lutely and relatively, than in S. ansoiili. The base of the tail is thicker, and 

 its least height measures as much as half the head length. 

 The forehead descends to the mouth in a sharp curve, so that 

 the snout is thick and rounded. The eye is relatively small 

 — one-fifth of the length of the head — is more than its 

 own diameter behind the snout, and twice its diameter 

 from the other eye. The maxillary bone is broad, and 

 extends below the middle of the eye. The cleft of the 

 mouth is short, and all the teeth in the jaws are smaller than 

 in the preceding type. The teeth on the vomer form two parallel series, with 

 a transverse row of six teeth in front (Fig. 148). The palatine bones are nearly- 

 straight, and converge forward, so that the palatine den- 

 tary arch is not parallel to the maxillary arch (Fig. 149). 



The edge of the pre-operculum is straight, and is 

 more perpendicular than in several forms. The sub- 

 operculum does not extend back behind the operculum, 

 and the lower borders of both these opercular bones are 

 nearly horizontal. There are ten to eleven branchiostegal 

 rays. The rake-teeth on the gill arches are long and 

 pointed, and the last arch carries ten rather long teeth. 

 The dorsal profile rises less rapidly than in the Common Trout, and sinks 

 less. The dorsal fin begins in the middle of the length, is a third higher than 

 long, and its edge is evenly truncate behind, so that the last ray is about half 

 as long as the longest ray. The adipose fin is somewhat long and high, and 

 reaches farther back than the end of the anal fin. The base of that fin is 

 only two-thirds as long as the base of the dorsal ; but the fin-rays are only a 

 little shorter. The ventral and pectoral fins are somewhat longer and more 

 pointed than in the Common Trout, the pectoral reaching back to the beginning 

 of the dorsal. The terminal rays of the emarginate caudal are three-quarters 

 of the length of the head. The scales are rather larger and stronger than 

 in S. ausonii, so that along the more strongly-curved lateral line there are 

 only about one hundred and three perforated scales. 



Accorduig to Meckel and Kner, the pyloric aj^pendages differ from those of 

 the Common Trout. The crown-shaped first row is the longest. The second 

 row rims in a curve on the intestine, recalling the condition in Coregonus. 



In colour this species resembles the pale varieties of the Common Trout. 

 The red and black spots are both intense. The red spots cover the operculum, 

 back, and sides of th(; body down to the caudal fin. After death the red spots 



Fig. 149. — VOMER PA- 

 LATINES AND MAXIL- 

 LARY ARCH OF SALMO 

 OHTf8IROSTRLS. 



