.SEA-BREAMS. 



57 



Obs. In order to coinprelifiid the mutual relations of the spe- 

 cies within this group of the genus Spams, it must be of interest 

 to sec liow far certain relations point to a fixed direction of deve- 

 lopment in the diiferenoe of species. In several respects, it is true, 

 this difEerence is connected with the difference in the depth of the 

 water where they live, and this consists, as usual, in the greater or 

 smaller size of the eyes. To a great extent, too, it may depend, as 

 we see in some of the corresponding circumstances in the Salmotiidai", 

 on the preponderating influence of se.x on the development, on which 

 point, liowever, we cannot give any opinion here owing to the lack 



of tlie necessary information. In other cases, on the contrary, the 

 difference in form runs parallel to the individual development, and 

 enables us to trace the natural, generic course of development. The 

 appended comparative table gives examples of the relations mentioned, 

 and simultaneously states the most apparent and constant characters 

 of three species represented by one specimen of Sparus mormyrus 

 (LinNjEUs's type-specimen of 8p. Imrta), one specimen of Sp. eri/tliri- 

 nus from Nice, kindly lent to mo by the Museum of Upsala Uni- 

 versity, and two specimens of 6'/). centrodontus, the younger from 

 Bohuslan and the nlder from the Atlantic outside Bergen. 



Ijenijtli of the body, expressed in mm 



Breiidth of tlic snout* in Ji of tlie length of the lower jaw 



,, ,, ,, .. ,. ., ,. ,. internrbitiil spacc^ 



Interorhital space ,. .. .. ,. length of the head _ ". 



Lengtli of the snout'' ,, ,, ,, ,. ., ., 



Base of the anal tin in % of the distance between the tip of the snout and the beginning of tlic dorsal tin. 



Horizontal diameter of the eye in % of the length of the body 



, head 



., snout ._ 



,, ., , breadth „ ,, iuterorbital space 



,, ,, ,, ,, ,, length ,, .. lower jaw 



,, ,, ,, „ ,. least depth of the tail 



of the length of the body 



„ ,, ,, .. ., head 



„ ,, distance of the dorsal tin from the ti]) of the snout 



of the base of the anal tin .- 



in % of the length of the body 



)i )» J? 



Length of the snout in % 

 Base of the aual fin ,. 

 Postabdominal leugthf,, 

 Breadth of the snout in 

 Postabdominal length 



Base of the anal tin „ „ „ .. .. ,. .. .. 



Least depth of the tail ,, „ ,. .. .. ,, ,, „ 



Length of the pectoral fins ,, ,, ,, ,. ,, ,, ,. , 



,, ,, ,, ventral fins in % of the length of the pectoral fins. 



Sparus 

 mormyrus 



248 

 !i3.(i 



71,4 

 2.S.4 

 51.3 

 41.4 



.5.7 



19 



37 



G(5.« 



50 



tiO.'.i 



15.3 



55.4 



(14.6 



3l).G 



25.8 



Vi.h 



it.2 



23.0 

 70.0 



tryth rinvs 

 224 

 51.il 

 (id.r, 

 31 

 4;!.4 

 48. s 



7.4 



24.3 

 56 



78.(; 

 61.1 



114.3 



13.1 



57.3 



69.r, 



36 



25.4 



17.4 

 7.8 



33 



51.7 



292 

 50 



61.5 

 31.7 



m.r, 

 53.3 



8.2 



29.2 

 96 

 92.3 

 75 



KX) 



8.G 



68.3 

 78.1 

 28.6 

 28.1 

 19.1 



8.2 



29.4 



57 



333 

 48.7 

 5(;.2 

 33 

 80 

 54.7 

 8 

 27.3 



91.4 



82.8 



71.6 



96.4 



8.7 



66 



77.8 

 28.1 

 27.3 



19.2 

 8.2 



30 

 54 



The differences arising from the direction of development com- 

 mon to the whole genus, expressed in their proportions, run uni- 

 formly through all these four columns, rising or falling. The other differ- 

 ences are those with regard to whicli we have to look for the grounds 

 for the interruption of the serial arrangement in local or sexual circum- 

 stances. The comparison shows that Spavva inormi/i'us, which lives 



in the shallower parts of the Mediterranean, seems in its characters 

 to come nearest the original type of the genus, which might have 

 been especially distinguished by smaller eyes, shorter pectoral fins 

 and a higher cheek, as well as a higher peduncle of the caudal fin. 

 This species is also distinguished by the transverse bauds, which call 

 to mind the juvenile colouring of other species. 



" Smitt: Kritisk Forteckning ofvev de i Riksmuseum befintUga Salmonider, K. Vet.-Akad:s Handl., Bd. 21, X:r 8. 



' The breadth of the snout here, as everywhere in this work where nothing else is remarked, is measured across the outer edges of 

 the knobs of articulation of the maxillaries. 



' The breadth of the interorbital space here represents the breadth of the forehead from one orbital margin to the other, across the 

 middle of the eyes, and is thus far from alwa3's the least breadth of the forehead. 



'' The length of the snout is measured from the anterior margin of the orbit to the middle of the tip of the snout. Steindachnek 

 (1. c.) has evidently taken this measurement in another way. 



'■ As in the treatise on the Salmonid.T of the Royal Museum mentioned above, I give this name to the distance between the foremost 

 point of the insertion of the ventral fins and the beginning of the anal. 



Scondinavia7i Fisht 



