1884.] ON RACES AND HYBRIDS AMONG THK SALMONID^. 17 



from St. Vincent, but is I think sufficiently distinguished by the 

 following characters : — the fine acute spines of the |)enultimate and 

 terminal segments are here replaced by conical or rounded tubercles, 

 and the posterior half of the antepenultimate segment, wliich is 

 represented as smooth and entire in G. bradiji, is granulated in 

 G. trachurus on the dorsal surface and minutely spiuulose on the 

 posterior margin. 



EXPLANATION OP PLATE I. 



Fig. 1. Callianassa martensi, sp. n., male, X I5 diam. (p. 13). 



la. Frontal region and antennte of the same species, showing the form of 



the frontal spines, X 3 diam. 

 1 b. Extremity of one of the legs of the third pair, showing the form of the 



produced posterior lobe of the penultimate joint and of the dactylus, 



X 4 diam. 



1 c. Terminal segment and uropoda, X 3 diam. 



2. Terminal segment and uropoda of C. mauritiana, enlarged. 



2 a. Larger chelipede of Callianassa mauritiana, Miers, natural size. 



3. Gonoductylus trachurus, v. Martens, adult male, x2 diam. (p. 16). 

 Za. Eaptorial limb (second masillipede) of the same species, x 3 diam. 



4. On Races and Hybrids among tlie Salmonid<^. 

 By Francis Day^ F.Z.S. 



[Eeceived December 24, 1883.] 



In March 1882 I laid before the Linnean Society the results of 

 some observations which I had made on the British Salmonidae, 

 tending to show that the number of species existing in these islands 

 had been unduly multiplied by local races or varieties having been 

 considered species. In the month of December I communicated to 

 this Society some facts respecting the hybridization of Salmon and 

 Trout, and likewise adverted to Sir J. Gibson- iVIaitland, Bart., F.L.S., 

 having kindly instituted, on November 15th, 1882, three fidditional 

 experiments upon crossing different forms of Charr, or Charr with 

 Troiit, the results of which, so far as they have gone, I propose 

 describing this evening. 



I have also to thank Sir J. Gibson-Maitland for permitting me to 

 take examples of all the various crosses which have been made at 

 Howietoun (many of which are on the table for examination), while 

 lie has also freely furnished me with information on all points, and 

 access to his notes. There are likewise a series of Salmonidae hatched 

 in the great International Fisheries Exhibition, from eggs brought 

 from Canada by Mr. Wilmot, the Canadian Commissioner, who gave 

 me specimens at short intervals, so that I have a connective series. 

 I shall have to refer to a pair of fine Trout sent to me in ice from 

 the Otago Acclimatization Society, through the kind ofKces of Air. 

 Arthur, which are now preserved in spirit in the Economic Fish 

 Museum at South Kensington. Lastly, I shall describe the Salrno 

 gracilis of Couch (? Cuv. & Val.), a local race which I had the 



Pkoc. Zool. Soc — 18H4, No. U- 2 



