1868.] ON THE DEVELOPMENT OF THE SALMON. 247 



(thirdly) a small canine, (fourthly) a very large canine fitting into 

 a groove of the upper jaw, (fifthly) at some distance from the 

 preceding a smaller canine corresponding to the upper posterior 

 canine, and followed (sixthly) hy a series of closely set small teeth*. 

 The upper jaw overlaps the lower slightly, the maxillary extend- 

 ing far behind the eye, which is rather small, placed in the middle 

 of the depth of the head, nearer to the snout than to the gill- 

 opening. Suborbital slightly and irregularly striated. Origin of 

 the dorsal fin nearer to the end of the snout than to the root of the 

 caudal, its last ray being opposite to the origin of the anal fin. 

 Pectoral extending beyond the root of the ventral, ventral scarcely 

 reaching the vent. Operculum very narrow ; a naked space be- 

 tween the suborbital and lower limb of the opercle. Coloration 

 uniform ; a black spot on the end of the lateral line. 



Two examples, 10 inches long, were collected by Mr. Bartlett at 

 Xeberos. 



Tetragonopterus melanurus, B1. 



Specimens from Surinam have the caudal fin whitish, with a 

 broad black median band. 



Myletes duriventris, Cuv. 



D, 15-16. A. 33-34. Abdominal spines 39-48. Xeberos. 



Cynodon pectoralis, Gthr. 

 D. 45-48. Xeberos. 



XiPHORHAMPHUS FALCIROSTRIS, CuV. 



A. 22-27. Young, with a blackish longitudinal band. Xeberos, 

 Pebas. 



6. On the Supposed Arrest of Development of the Salmon 

 when retained in Fresh water. By James Murie, M.D., 

 F.L.S., F.G.S., Prosector to the Society. 



(Plate XXIII.) 



Introductory Uemarks. — Lately there was brought to me a small 

 fish of which the life-history is somewhat peculiar. So interesting, 

 indeed, does it seem to me that I have not hesitated in bringing the 

 facts of the case before the notice of this Society. I do so the more 

 readily because it appears to me that, if it could be shown with 

 certainty that the said fish is an undoubted Salmo salar, Linn., 

 a physiological law of wide import would necessarily follow. 



* I have given this detailed description of the dentition because the other 

 species referred to Ci/nopofaynus have another series of small teeth within the 

 outer. This is another proof that Cynopotamiis is not a distinct genus. 



