1012 
SCANDINAVIAN FISHES. 
and has the form of a flattened cone. High up on the 
superior arms of the clavicles are attached the scapular 
disks. These are thin and in great part cartilaginous, 
each consisting of a circular scapular part (fig. 265, sc), 
with an angular incision above and a small, round hole 
(scapular fenestra) below, and a semicircular coracoid 
part (fig. 265, cr), both of them fitted into the mem- 
brano-cartilaginous disk. A scapular disk as simple as 
this belongs to the earliest stages of development in 
other Teleosts; but a manifest relic of the morphological 
alliance with more primitive piscine types appears in 
the great number of supporting bones (brachial bones 
— fig. 265, b) possessed by the pectoral fins of the Eels. 
In almost all" the preceding Teleosts the number has 
been 4; in our common Eel it is 7 or 8. Anna, a Gan- 
the primitive forms. The loss of the ventral fins, on the 
other hand, as we have seen in many of the preceding Te- 
leosts, is, here too, secondary in its significance; and in 
foreign Eels the pectoral fins may share the same fate 0 . 
The skeleton of an adult Eel is firmly ossified, and 
characterised by its numerous vertebrae ■ — generally 
more than 100, sometimes about 160 — of almost uni- 
form shape and with feebly developed appendages. In 
our common Eel the anterior vertebrae, to the seventh 
inclusive, have their shallow but long, almost contiguous 
neural spines broken up into several (as many as 9) 
spicules'*. The said vertebrae are furnished both with 
upper" and lower-' transverse processes. The former are 
alary spines, directed backwards and of fairly uniform 
strength, which are, however, exchanged on the seventh 
Fig. 266. Three abdominal vertebra; (44 — 46) in Anguilla vulgaris , seen from the left and magnified. 
na, scleral bone (epinenral, cf. fig. 236, p. 947); psps, upper spinous process; ptrp, lower posterior transverse process {processus transuersus 
posterior ); ptra, lower anterior transverse process; ha, haemal arch; pspi, lower spinous process {processus spinosus inferior)', pi, ribs. 
oid genus, has the same number; and Polypterus, an- 
other Ganoid genus, has 13 — 17 brachial bones. These 
Ganoids have besides retained one or more bones be- 
longing to the innermost (proximal) row of the prim- 
ordial cartilage (Gegenbaur’s pterygium) of the pectoral 
fins, which has entirely disappeared in the Teleosts. 
During the evolution of the Teleost type the basal parts 
of the pectoral fins have thus suffered reduction 6 ; and 
the Eels are most nearly approximated in this respect to 
and following vertebrae for scleral bones, directed back- 
wards and upwards in the dorsal half of the great lateral 
muscle (fig. 266, na). The lower transverse processes 
(ptra) of the first vertebra are only small, pointed pro- 
tuberances. On the following vertebrae they grow 
broader, but from the seventh vertebra inclusive they 
become pointed spines, directed outwards, backwards, 
and downwards, and bearing at the tips short and weak 
ribs (pi), which in their turn give place towards the 
a For exceptions see the Batrachoids (p. 133, above) and the Lophioids (p. 136). Ostracion, a Plectognate, has 5 basal bones. 
5 Cf. Smitt, Ur de hogre djurens utvecklingshistoria, pp. 222 seqq. 
c Cf. the Lophobranchs, see above, pp. 667 seqq. 
d In the Conger this division is restricted to the formation of lateral grooves on the neural spines, but is perceptible in this form 
even in the 13th vertebra. 
e Diapophyses. 
f Parapophyses. 
