102 M. Fries on the Genus Syngnathus. 



6. The rays of the dorsal fins vary, it is true, in number, as is 

 the case in most fish ; but the difficulty of counting them with 

 certainty renders the character which might hence be adduced 

 less appUcable, and is undoubtedly the chief cause of the 

 different statements which we find in various authors re- 

 specting their number. To be able to determine the number 

 with certainty, the fins must be spread out under water, and 

 the rays counted with the help of a lens. 



7. The colour of the body is quite characteristic for our na- 

 tive species, if they are examined when alive, although, as in 

 most fishes, it is subject to great variation with respect to 

 markings and depth. The colour is, however, for a diagnosis 

 of a second-rate value, since in order to determine it, it is ne- 

 cessary to have live specimens at hand. It is impossible to 

 judge of the colour of a living specimen from one which has 

 laid in alcohol. 



8. The length of the snout, in proportion partly to the length, 

 partly to the height of the head, I regard as being the cha- 

 racter most easily seized for distinguishing the species, and 

 shall therefore especially employ this character in the diagnoses. 

 The distinction is very perceptible, and indeed no measure- 

 ment is necessary : but in order to determine distinctly this 

 character by terms, and to leave no room for doubt respecting 

 the scale of measurement, I w ill previously explain that I take 

 the length of the snout from its extremity to the centre of the 

 eye, and compare this length with the distance from the cen- 

 tre of the eye to the posterior edge of the operculum. I am 

 convinced from numerous comparisons that this character is 

 constant in both sexes and in specimens of different size and 

 age of the same species. 



In order to distinguish our three native species in the easiest 

 way, they may be divided as follows into two sections. 



• Pinna caudali rudimentaria e radiis a brevissimis composita {parte ma- 

 jore pinncB dorsalis ante latitudlncm ani sita.) 



To this section belongs only one species. 



-^QUOREAL FiTE-FtsH, Syjigiiathus cequoreus, Linn. — Trunco sat distincte 

 aiigulato ; longitudine rostri distantiam a centro oculi ad margincm 

 operculi superaxite. 



Syn. S. aequoreus, Linn. Syst. Nat. i. p. 417; Mont, in Wern. Mem. i. p. 



