358 ADDENDA. 



2. $. irideus, Gibbons. PACIFIC BkooK TROUT. Form 

 stout; head short, bluntish; mouth small, the maxillary 

 scarcely reaching beyond eye. Streams W. of Sierra 

 Nevada. (S. newberrii, Grd., S. masoni, Suckl.) 



aa. Scales small, in 165 205 rows. 



6. Caudal somewhat forked; head small, conical, rather 

 pointed. 



3. S. tsuppitch, Rich. BLACK TEOUT OF LAKE TAHOE. 

 Rather slender; mouth moderate; opercle prolonged 

 backwards; scales in 180 rows. Streams W. of Sierra 

 Nevada. 



bb. Caudal double-rounded ; head heavy, shortish, convex. 



4. S. spilurus, Cope. BIG-MOUTHED TROUT. Mouth 

 very large, the maxillary reaching much beyond eye; 

 opercle not specially prolonged; black spots most numer- 

 ous posteriorly. Rocky Mountain region, Wyoming to 

 Arizona. 



9 



Var. pleuriticus, Cope. Scales small, in 200 rows; 

 head carinate. Generally distributed. 



Var. spilurus, (Cope). Scales larger, in 170 rows; 

 he&d strongly convex. Utah to Colorado, etc. 



f Hyoid bone with an elongate band of small teeth (easily 



scraped off by careless observers). 



c. Head large and long acuminate ; hyoid teeth weak ; cau- 

 dal somewhat forked. 



5. S. henshawi, G. & J. (sp.n.) SILVER TROUT OF LAKE 

 TAHOE. Head little carinate; body elongate, not much 

 compressed; scales in 160 184 rows. Streams of Cal. 



cc. Head comparatively short and blunt ; hyoid teeth rather 

 strong ; caudal less forked. 



6. S. sfom/as, Cope. Scales in 200 rows; head broad 

 and flat. Upper Missouri. 



