92 
SCANDINAVIAN FISHES. 
b: Hind portion of the body and 
the belly also covered with 
scales. Subgenus Sarda Sarda pelamis. 
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 Auxis Auxis 1 hazard. 
B: Hind portion of the body and 
the bellv also covered with scales. 
Genus Scomber Scomber scombrus 
Genus ORCYNUS. 
Body terete and fusiform. In the preabdominal region the scales of the body form a corslet of larger and more 
firmly fixed scales than on the rest of the trunk. Dorsal fins but little apart from each other , both the anterior 
and the posterior being highest in front and pointed , with the upper margin deeply concave: second dorsal fin 
(i excluding the finlets ) situated, either completely or to a great extent, in front of the anal, which it closely re- 
sembles in other 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 a . Pectoral fins on a level with or sometimes below the eyes. Adipose eyelid 
comparatively little developed. The preorbited bone leaves the broad, back part of the upper jaw-bone for the most 
part visible, when the mouth is closed. Jaw-teeth small. On each side of the tail a high, longitudinal middle 
carina without scales, and at the base of the caudal fin two lower and shorter carince, covered with scales and 
posteriorly converging, one above 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 °/ 3 ) the 
length of the snout and greater than the height of the posterior dorsal. Depth of the anal fin about 2 / 3 {from 
60% to 70%) of the length of the ventral, which is more than 2 / 3 {from 70 % to 84 %) of that, of the pectoral. 
Length of the head less than half the distance from the tip of the snout to the second dorsal fin. Eyes of 
average size. Palatine bones and vomer toothless as a rule, at least the latter, or with small deciduous teeth 6 . 
Hcemapophyses of most of the caudal vertebree broad at the base and pierced by a large hole which in the anterior 
part of the tail is so wide that the whole of the hcemapophyses resembles a network hung beneath the bodies of 
the vertebree. 
To Lutken belongs the merit of having first given, 
in his Spolia Atlantica, both the external and internal 
characters which mark this subgenus, which he named 
Thynnus s. str., a title which he subsequently c ex- 
changed, however, for Euthynnus. The reduction of 
the palatine teeth and the scales of the body, as well 
as the comparatively small size of the head and the 
great height of the first dorsal fin, seem to indicate 
a During youth the number of anal finlets is only 7 ; and aec 
tail, both above and below. 
b According to Moreau, Euthynnus allittercitus has teeth both 
rine teeth in his specimen. According to Collett there are neither 
always to be without vomerine teeth. 
c See Jordan and Gilbert, Syn. N. Amer. Fish., Bull. U. S. 
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, Euthynnus takes the lowest rank among 
the Tunnies and stands almost on the same level as 
irding to Ruppell, in Ovcynus bilineatus there are only 6 finlets on the 
on the palatine bones and on the vomer. Steindaohner found no vome- 
pnlatine nor vomerine teeth in this species. Euthynnus pelamis seems 
Nat. Mus., No. 16, p. 429. 
