1082 



SCANDINAVIAN FISHES. 



sul)<)i'l)ital (preorljital) margin ut'the Teleosts; hut it caii- 

 iiot be fully homologous therewitii, tor here the nostrils 

 are situated below it. The nostrils, which lie Justin front 

 of the median upper lij), are externally — each being 

 bounded laterally by the lateral upper lip of that side^ — 

 simple, round, and rather large apertures, separated by 

 a thin sei)tum. On raising the lateral upper lip we find, 

 liowever, that each nasal cavity besides possesses a pos- 

 terior opening, a dermal fold, bent into several curves 

 and internally supported by a cartilaginous disk (fig. 

 294, In.,), being turned inwards from the outer margin 

 of the nasal cavity and foi'ining the greater part of the 

 posterior limit of the anterioi' nostril. To meet the inner 

 edge of tliis dermal fold — ■ though without being con- 

 tiguous with it — a longer fold rises from the inner 

 margin of the nasal cavity, a true narial passage being 

 thus present, though not fully closed behind". Exter- 

 tially the nasal cavity is covered by the lateral upper 

 lip, so that the posterior nostril opens within the lip, 



Fiir. 304. .Jaw-teeth of the left side in tlie Nortlicrn Cliiinivra (CTi'miPca 

 monstrnsn). After Ag.^SSIZ. A, seen from -without; B, from within. 

 da, anterior dental plate of the upper jaw; dp, posterior dental plate of 

 the same; di, dental plate of the lower jaw. Cf. fig. 294 (p. 1065). 



inside the cavitj' of the mouth. The Chinia}ra can 

 thus respire even when the mouth is closed. 



The lips are thick and fleshy, studded outside and 

 at the margins with small protuberances (papillae), the 

 upper lip, as we have already hinted, being divided 

 into three parts, a quadrangular middle part (median 

 upper lip) and two larger wing-shaped lateral lobes (la- 

 teral upper lips). The median uiijier lip as well as the 

 underlip is doultle. The former partially covers the two 

 anterior dental plates (fig. i'dA, da) of the upper jaw. 

 Tiie underlip is entire in front, but furnished behind 

 witli a broad, pendent fla]) at each corner of the mouth. 

 Tiie dentition of the mouth consists of two pairs of 

 palato-dental i)lates, one pair (figs. 294 and 304, da) 

 before the other ((///), at tiie margins of the upper jaw, 

 and a single pair of mandibular plates {di). The inter- 

 maxillary (prepalatine) plates {da) are quadrangular and 



most distinctly grooved, with 6 rounded ridges: the lateral 

 maxillary (palatine) plates (dp) and the mandibular plates 

 {di) are more triangular, undulate and nodose on the 

 inside. The tongue is small, but free at tlie ti]), and is 

 densely set with papilla?. The front of the branchial arches 

 is also studded with similar papilla;; but soft gill-rakers, 

 about 12 on the first branchial arch, are besides present. 



Tiie three free gill-arches are complete (with bran- 

 chial lamella; on both sides), but both before and behind 

 them lies a half gill (single row of laraella;), the former 

 coalescent with the operculum, the latter with the hind 

 (abdominal) wall of the branchial cavity. The gill- 

 openings are about equal in dejith to the length of 

 the orbits, and are set far down, though separated by 

 an isthmus the breadth of which is about equal to the 

 depth of the orbits. 



The general form of the fins we have already no- 

 ticed. The triangular first dorsal begins just behind the 

 head, the length of which varies between 80 and 90 % 

 of the distance from this fin to the tip of the snout. 

 The spine at its anterior margin lies exactly above the 

 base of the pectoral fin and sometimes (in the male.s) is 

 oidy a little shorter than the head; sometimes (usually 

 in the females) only ""/j as long. It is rather sharp in 

 front and is marked anteriorly on each side •with a 

 distinct groove. Both its posterior margins are armed 

 superiorly, usually somewhat more than half-way down 

 the spine, with pointed, descending prickles, and its top 

 is usually free from the remainder of the fin to a point 

 a little further downwards. Behind the spine the fin is 

 supported by fibrils, gathered into about a dozen sepa- 

 rate bundles, which resemble fin-rays. The posterior 

 margin is somewhat concave, and the fin-membrane is 

 prolongated to the vanishing point backwards along the 

 dorsal margin and more or less near to the second 

 dorsai tin. The latter tin begins at a distance from the 

 tip of the snout measuring a little more or less than 

 twice the length of the head and extends back about 

 half-way along the rest of the liody, measured from the 

 commencement of the fin. Its height is almost uniform 

 and only about V4 or '/j of that of tlie first dorsal. 

 Just liehind its termination the upper caudal lobe begins. 

 The lanceolate caudal fin is made up (jf two almost si- 

 iniL'ir lobes, one over and one under the tail, whose tip 

 nari'ows uniformly to a filament, and of which they 

 occupy the anterior half or third, before thej' gradually 

 and, at last, imperceptibly disappear. The anal fin con- 



" Answering to one of the stages in the development of the nostrils of the high( 



