718 



SCAXDINAVIAX FISHES. 



without transverse processes; hut the fourth, when its 

 hody is distinct from that of the third, not only pos- 

 sesses a rih-likc transverse process on each side, united 

 by a suture to this side and both set and curved in 

 the same direction as the ribs, only shorter and more 

 terete tlian tlicv, Init also bears on its under surface 

 Mil inner, lamellar process, set transvei'sely and united 

 to tlie bod^■ of tlie vertebra and to the transverse 

 ])rocesses, pierced at the base (like an hypapophysis), 

 iind curved backwards and downwards behind the tip of 

 tlie large pharyngeal jirocess of the occipital bone. To 

 tiie po.sterior surface of this inner process of the fourth 

 vertebra is attached the centre of the anterior end of 

 the air-bladder, and the passage in its Imse receives the 

 aorta and the anterior end of the kidneys. According 

 to Sagejieiil" this process also belongs to the fourth 

 vertebra in Hi/droci/on (a Characinoid) and originates 

 from the ventral and partly from the lateral sides of 

 the body of this vertebra''. In tiie Barbel, where, as 

 we have mentioned, the body of the fourth vertebra 

 coalesces witii that of the third, we see, however, that 

 the roots of this process lie on the anterior part of this 

 composite body, thus within the limits of the third ver- 

 tebra. A removal in a backward direction thus seems 

 to have taken place in the rest of our Cyprinoids, an 

 assumption which tinds further ground in the insertion 

 of the hindmost so-called acoustic bone {malleus) between 

 this process and the true transverse process of the fourth 

 \ertebra to join the wall of the air-bladder. Here, as in 

 the Sheattish (see above, \>. 699), we explain the malleus 

 on each side as the transformed rib of the third vertebra. 

 In the Cyprinoids it is crescent-shaped or, rather, like 

 the blade of a headsman's axe, and at the inner (con- 

 cave) margin is set the process whereby it articulates 

 with the side of the body of the third vertebra. Its 

 anterior end, which is united by a ligament to the so- 

 called stapes, ]3rojects abo\e the base of the transverse 

 process of the second vertebra. This last vertebra sends 

 out to the ligament just mentioned the bone which has 

 been called the incus, a l)onelet bitid at the base and 

 with one branch articulating in a hole in the bodj- of the 



second vertebra and the other united by a ligament to the 

 same bone. The incus on each side is explained as the 

 transformed rib' and neural arch of the second vertebra. 

 The two anterior among the so-called acoustic bones, 

 the stajics and claustrum. wliich lie close to each other 

 on the covering membrane of the atrium sinus imparis 

 (see above, p. G99), are partly foliate in form, and are 

 explained as re])rf'senting on each side the otherwise want- 

 ing neural arch and spine of the iirst vertebra. The se- 

 cond vertebra is apparently Avithout neural sjnne (upper 

 spinous process), l)ut its place is taken by a covering 

 bone above the spinal canal between the occipital bone 

 and the large neural spine of the third vertelira, which 

 spine is usually strengthened by coalescence \vith the 

 neural spine of the fourth vertebra. 



In the structure of the head we shall here remark 

 only the comparative])- perfect development of the or- 

 l)ital ring. Not only do the ordinary (here 4 — 8) sub- 

 orbital bones surround the eye behind, below, and in 

 front; the ej'e is also protected above by a supraorbital 

 bone, a covering bone on the frontal bone of each side. 



The skeleton of the Cyprinoids, which as a rule 

 contains a moderate number of vertebra; (40'' — 50), is 

 further distinguished by the high and upright, anterior 

 and upper, articular processes (zygapophyses) of the ab- _ 

 dominal vertebra\ especially in the forepart of the trunk, ■ 

 where the top of each of these processes meets the base 

 of the neural spine of the vertel)ra immediately in front 

 or the upper part of the neural arch of this vertebra.' 

 The shoulder- girdle is strong. The incurved anterior mar- 

 gin of the clavicle ma}' sometimes, as in Laheo', he de- 

 veloped into a disk so broad that only a narrow passage 

 is left for the a'sophagus. The coracoid bone is also as a 

 rule comparatively broad, and the precoracoid bone 

 ascending from the upper margin thereof, is bifid at the 

 top, one bi-anch meeting the clavicle, the other the sca- 

 pula. Tlie iK'lvic bones nvc elongated, in front bitid, 

 sometimes for the greater part of their length, liehind 

 united by cartilage or a suture. From a morphological 

 point of view the articulation of the ventral fins is in- 

 teresting, as Davidoff has shown', on account of its 



" Morphol. JaLrb., Bd. X (1884), p. 55. 



*■ Sagemehl explains it as a transformed pair of ribs belonging to this vertebra. Sorexren, wlio calls it os suspetisorium, ascribes it 

 to an ossification of the wall of the air-bladder. Cf. S.igemehl's explanation of the pliaryngeal process of the occipital bone (see above). 



'■ Ligamentous ossification, according to SoEENSEN, Om Forbeninger i Svemmeblaren etc., Dsk. Vid. Selsk. Skr., 6:te Ra>kke, Naturv., 

 Matli. Afh., B. 6, No. 2, p. 41 (scp.). Tlie said paper did not reach me, unfortunately, until tliis sheet was in the press. 



'' In Barbus inaculattis, according to Gl'nther, 30. 



' GtiNTHEE, Cat., VII, p. 47. 



/ Morphol. Jahrb., VI (1880), p. 4G4, taf. XXI, fig. 4. 



