SC0MBR01DS. 
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THE PLAIN PELAMIS. 
ORCYNOPSIS UNICOLOR. 
Fig. 29. 
Back dark steel-blue. Belly silvery. No distinct stripes or bands in the colouring of the body (in adult speci- 
mens). Mandible about as long as the base of the anal fin or the length of the pectoral , or even a little shorter 
than the latter. 
Fig. 29. Plain Pelamis ( Orcynopsis unicolor), from Bohuslan. J / 4 natural size. 
R. hr. 7; D. 13/— 2 /VIII; A. 2 /VII; P. 2 1. 3 + 21; 
'll 1. 12 ’ 11 1. 12' 
V. V 5 ; C. « + 17+». 
Sjn . Scomber unicolor , Geoffr., Descr. de I’Egypte, Poiss., tab. 24, 
fig. 6(?); Gthr ( Pelamys ), Cat. Brit. Mas., Fish., vol. II, 
p. 368; Gill ( Orcynopsis ), Proc. Acad. Nat. Sc., Pliilad., 
1862, pp. 125 et 126; Cedf.rstrojvi ( Pelamys ) Of vers. Vet.- 
Akad. Forb. 1876, No. 4, p. 64; Sundstrom, Fn. Sverg. 
Ryggr., p. 227; Coll, ( Orcynopsis ), Vid. Selsk. Fork. Christ. 
1879, No. 15, p. 3; Gigl. ( Pelamichtliys ), Espos. Int. Pesc. 
Berk 1880, Cat. Sez. Ital. , p. 85; Lillj., ( Orcynopsis ), 
Sv., Norg. Fisk., vol. I, p. 266. 
Cybium Bonaparti, Ver., Att. 8:va Riun. Scienz. Ital. Genov. 
1846, p. 493; Fir., et Ver. {Pelamys), Mem. R. Accad. Sc. 
Tor., ser. 2, tom XVIII, p. 194, tab. fig. 4; Mor., Hist. 
Nat. Poiss. Fr., vol. II, p. 434. 
Thynnus peregrinus, Coll., Vid. Selsk. Forb. Christ. 1879, 
No. 1, p. 20, tab. 1, fig. 1. 
Obs. Whether Ruppel’s Thynnus {Pelamis) unicolor a is iden- 
tical with this species, as Lutken 6 thought probable, cannot yet be 
decided. The difference in colour — the glossy, reddish violet of the 
belly, and the white tips of the second dorsal and the anal fins in 
Ruppell’s form — as well as the difference in the fin formula — one 
ray more or less in the first dorsal ■ — is certainly unimportant 
when we consider the similarity in other respects. But the compa- 
ratively long ventral fins and the low anterior dorsal in Ruppell’s 
figure would form more important distinctions, if one could rely on 
these points when there is no mention of them in the description, 
and when they are possibly differences of sex or age. The great 
difference which we see in Ruppell’s figure between the length of 
the lower jaw and the base of the anal fin, which is considerably 
shorter, is also worthy of notice. 
The Plain Pelamis, which attains a length of about 
8 dm., is fairly elongated in form, like the following 
species, but more compressed than the true Tunny. 
The character, too, which is expressed in the small 
extent of the corslet, is common to both the species 
of Pelamis; but in the Plain Pelamis a belt of scales, 
starting from the corslet, runs along the whole of the 
lateral line, which is more even and less undulating 
in its course than in the Striped Pelamis. In compa- 
rison with the latter the hind part of the body is more 
elongated, the beginning of the second dorsal tin being 
situated in front of the middle of the body. The 
corslet is less marked than in the Tunny, but similar 
in form, with clearly defined sinuses at the beginning 
of the lateral line. The uppermost sinus extends for- 
ward along the side of the back to the gill-opening, and 
above it the scaly covering of the body follows the bases 
of both dorsal fins; the second sinus extends forward 
“ Neue Wirbelth., IV, ( Fische cl. Rothen Meeres), p. 40, tab. 12, fig. 1 — Pelamys nuda, Gthr, Cat., ]. c.; Klunz., Verh. Zc>ol. 
Bot. Ges. Wien, 21 (1871), p. 443. 
b Spot. Atl., 1. c., p. 477. 
