92 



SCANDINAVIAN FISHES. 



It: Hind portion of the body and 

 the belly also covered with 

 scales. Subgenus Sarda Su7'da pelaniis. 



II : The preorbital bone completely 

 covers the front part of the upper 

 jaw-bone and at least the greater 



portion of the back part, when the 



mouth is closed : 



A: Hind portion of the body and 



the belly for the most part naked. 



Genus Aiuvis Aiuiis thazard. 



B: Hind portion of the body and 



the belly also covered with scales. 



Genus Scomber Scomber scombrus. 



Genus ORCYNUS. 



Body terete and fusiform. In the iireahdominal region the scales of the body form a corslet of larger and more 

 firmly fixed scales than on the rest of the trunk. Dorscd fins but little apart from each other, both the anterior 

 and the posterior being highest in front and pointed, irith the upper margin deeply concave: second dorsal fin 

 {excluding the finlets) situated, either completely or to a great extent, in front of the anal, which it closely re- 

 sembles in otJicr respects. Height of the anal greater than the length of its base. Number of finlets behind the 

 dorsal and anal fins from 7 to 10". Pectoral fins on a level with or sometimes beloiv the eyes. Adipose eyelid 

 comparatively little developed. The preorbital bone leaves the broad, back part of tJie up)per jaiv-bone for the most 

 part visible, when the mouth is closed. Jaw-teeth small. On- eacli side of the tail a high, longitudinal middle 

 carina without scales, and at the base of the caudcil fin two lou-er and shorter carina, covered with scales and 

 posteriorly converging, one cdjove and one below the middle carina. Pyloric appendages numerous and sometimes 



united into a glandulous mass. 



Subgenus EUTHYNNUS. 



Body behind the corslet naked (without scales). Height of the anterior dorsal fin almost double (at least °l^) the 

 length of the snout and greater than, the height of fhe posterior dorsal. Depth of the anal fin about "/.^ {from 

 (10% to 70 9o) of the length of the ventral, which is more than Vs if ram 70 % to 84 %) of that of the pectoral. 

 Length of tin- liead less than half the distance from the tip of the snout to the second dorsal fin. Eyes of 

 average si^e. Palatine bones and vomer toothless as a rule, at least the latter, or with small deciduous teeth''. 

 HcBmapophyses of most of the caudal vertebrce broad at tJie base and pierced by a large hole which in the anterior 

 part (if the tail is so wide that fhe n-hole of the hwmapophyses resembles a network hung beneath the bodies of 



tlte vertebrce. 



To LuTKEN belongs the merit of having fii'st given, 

 in his Spolia Atlantica, botli the external and internal 

 characters M-hidi mark tliis subgenus, which he named 

 Thynnus s. str., a title which lie subsequently'' ex- 

 changed, however, for Euthynnus. The reduction of 

 the palatine teeth and the scales of the body, as ^vell 

 as the comparatively small size of the head and the 

 great height of the first dorsal fin, seem to indicate 



that in the development of the Mackerel-type it is this 

 group that has advanced farthest in the direction of 

 the Tunnies, though none of the species known attain 

 so great a size as the true Tunnies. In other respects, 

 however, as for example in the comparatively small 

 height of the anal fin and the fairly great length of 

 the ventral, Euthy)inus takes the lowest rank among 

 the Tunnies and stands almost on the same level as 



" During youth Wu- number of anal finlets is only 7; iuul aceortling to Ruppell, in Orci/iiux hilineatiis there are only G finlets on the 

 (iiil, botli above and below. 



'' According to MoitHAU, Euthyimns allitteratus has teeth both on the palatine bones and on the vomer. Steindachnee found no vome- 

 rine teeth in his specimen. According to Collett there are neither palatine nor vomerine leetli in this species. Enthi/untis pelamis seems 

 always to he without vomerine teeth. 



'■ See JoiiiJAN and Gii.nEr.T, S'/n. N. Amer. Fi.^^/i., Bulb U. S. Nal. ^lus., No. 10. p. 429. 



