552 



SCANDINAVIAN FISHKS. 



To judge by these materials, Onos fttsciis iiiust, therefore, be | that imist bo more aufl more pronoiiiiccd, the nearer the forms which 

 rec^arded as the type of the lowest stage of development among the | have the same origin, approach to tlie common original form. As this 

 Three-Bearded Rocklings, from which stage each of the otlier species 



has adopted a distinct direction; and the intermediate position men- 

 tioned above finds a natural explanation in the community of characters 



development of form helps us considerably to a correct understanding of 

 the characters incident to our Three-Bearded Rockling, we here give, in- 

 stead of a more lengthy description, the following table of measurements: 



55 V ?! 55 



ength of the body cxprcsseil in millimetres _ 



ength of the head - in % of the 



ongitudiual diameter of the eves ._- „ ,, ,, 



enst breadth of the iuterovbitiil spare 



ength of the upper jaw - - -.- 



., ,, louer ,, 



ostorbital leuirth of the head 



listanec between the first dorsal fin and the tip of the snout 



„ ,. second ,. ,, ,, ,, ,. ,, ., „ 



;o8c of the first dorsal fin 



„ ., second ,. „ 



.ength of the first ray of the first dorsal fin 



„ ,, longest „ ,, ,. second „ „ 



„ „ pectoral fins 



„ ., ventral - 



)istonce between the ventral fins and the beginning of the anal fin. 



„ anal fin „ ,. tip of the snout 



Jase of the anal fin 



jongest ray of the anal fin _ 



!^east deptli of the tail 



jength of the middle rays of the caudal fin 



Depth of the body at the beginning of the anal fin 



5reatest breadth of the head 



S'umber of rays in the pectoral fins 



„ „ 5- •• ventral ., 



length of the bodv 



»» H J> J) 



j» ji )j 



)) )) ?» 



jj )» » 



») ^ )? J5 



)» >» 



55 55 55 



55 55 55 



55 55 55 



Onoif fuscits 



164 



20.1 

 3.0 

 4.0 



10.4 

 11.3 

 12.4 

 17.!. 

 31.4 



12.1 



02.4 

 4.9 



9.1 



lO.G 

 ll.G 



30.. 5 

 46.3 

 38.1 



6,6 



4.9 



10.4 



12.8 



11.6 



15 

 (■) 



Q. 



Onos medlterrauens. 



Onos tricirratus. 





c" ■ o 



— . OS., 

 d OS - 



2= n 



<\ 



d Q0_, 



430 

 22.5 



2.3 



,5.1 

 13.0 



13.2 

 13.7 



21.1 

 32.5 



10.5 



,55.1 



2.8 



14.9 

 15.3 



26.7 

 44.2 

 40.7 



7.S 

 10.5 

 16.3 



19 



The Three-Bearded Rockling is the largest Scandi- 

 navian species of this genus, and attains a length of 

 about half-a-metre. Like the preceding species, it is 

 also one of the most typicid species of the genus, with 

 low and broad snout, the tip of which is naked, as the 

 scales of the head do not extend further fonvard than 

 to the line between the anterior nostrils. The posterior 

 nostrils are set nearer to the anterior ones than Id the 

 eyes — sometimes rather near the former — and are 

 Avithout any dermal flap, or have the margin evenly 

 raised into a short tube. Tlie cards of teeth in tlie 

 jaws and on the head of the vomer are broad and com- 

 plete. In young specimens the jaw-teeth are of uni- 

 form .size, but in older ones fairly large canines aj)- 

 pear, especially in front in the outermost row of the 

 intermaxillar}- teeth, and at the middle of the inner- 

 most row in the lower j;iw. Tiie card of teeth on the 



head of the vomer forms a more or less acute angle, 

 the sides of wliich run parallel to the interma.xillarv 

 bones, and occupies a space in the palate the breadth 

 of which is greater than the longitudinal diameter of 

 the eyes. The lower margin of the preorbital bones is 

 without barbels, but, especially in old specimens, we 

 often find this margin undulating in a manner that 

 reminds us of the most rudimentary lateral b;ir1>els in 

 the preceding species. The lateral line runs in a hori- 

 zontal direction rather near the dorsal maigin back to 

 the l)th or 10th pore, below the anterior part (if the 

 second dorsal tin, at which point it descends, reaching 

 the middle of the sides at about the 14th pore, and 

 then running straight back, but disappearing on the 

 hind i);\rt of the tail. Altogether we And 26 or 27 

 distinct pores in the lateral line on each side of the 

 body. Among the internal organs the air-ljladder is 



