AIUiVROl'ELECl'S OI.FEHSII. 



92/ 



larics. Each of its two brandies resembles iiii aciite- 

 ;iii"ii'il, isosceles triaiifj'le, with the short (hiiul) b;ise 

 turned (IdWiiwiirds, where the aiiguliir |);irt foriiis a 

 proiectiiig, spine-like angle. Within (above) and pa- 

 rallel to the thin lower niai'iiin runs a ridge on the 

 outer side. The symphysis is sti-aight, and projects 

 downwards in a chin-protuberance, channelled behind. 

 Most of the teeth in the lower jaw, which are also set ridge running from the aiitcn-ior ujjper corner down- 



\ertical arm of the rectangular jireopercujuin is about 

 tiiree times as long as the horizontal. The preoper- 

 lular angle is prolongated to a short, flat (thin), ti'i- 

 angular spine, pointing downwards. The other oper- 

 cular bones are cxtremeh' thin and tlexible. The 

 o]iercidum is rectangidai', but forms an oblique arti- 

 culation abo\c. its surface is obliquely crossed by a 



in a single row, are al)out twice as large as those in 

 tiie upiter jaw; but one of the anterior teeth on each 

 side is considerably larger than the rest, and at the 

 e.vtrcine front, where the teeth are of about the same 

 size as in the upper jaw, they are more distinctly ar- 

 ranged in a double row. The tongue is rudimentary, 

 and the cartilaginous tip of the hyoid bone is smooth, 

 without teetli. ()nlv the upper jaw is furnished with 

 a palatal fold, and this is not very broad. The vomer 



wards and baekwai-ds. Its lireadth is e((ual to the length 

 of the snout. .\t its lower margin lies the triangular 

 suboperculum, witii a more or less deep indentation 

 behind. Below the latter and below the preoj^ei-- 

 culum lies the interoperculum, wliich is divided into 

 two parts, the anterior (below the preoperculuni), 

 elongated and united with the branchiostegal mem- 

 brane only behind, the posterior quadrangular with 

 rounded corners or circular, and entirely coalescent 



is toothless, but on the anterior part of the palatine ! with the branchiostegal membrane, on which it lies 

 bones, as well as on the upper jjharyngeals, small teeth 

 iiia\' be felt. The pseudobranchia" on the inner surface 

 of the opercular and hyomandibular bones form an oblong 

 patch, in which about 14 filiform, transversely set la- 

 mella' may be counted. The gill-slits are large, ex- 

 tending far forward in the mouth; but the upper parts 

 of the hind branchial arches coalesce with the fi'ont side 

 of the scapular arch, the hindmost gill-slit thus being 

 closed above and rather short. The gill-rakers are long 

 hut scattered, luimbering about 14 on the first branchial 

 arch, besides a few small, hardly perceptible spines at 

 the lower (anterior) end. Where the horns of the hv'oid 

 bone touch the tij) of the basi-hyoid series (the lingual 

 bone), the}' are furnished with an erect protuberance. 

 The outer gill-openings are large, their upper angle 

 Iviiig on a level with the centre of the eyes, and the 

 branchiostegal membranes being free from the isthmus 

 and united to each other not quite to the full length of 

 the first branchiostegal rays, so that the anterior angle of 

 the openings lies in about a line with the tip of the snout. 

 The branchiostegal ravs are slender and rod-like. The 

 first si.x lie rather near each other, and the first of all is 

 set close to the corresponding ray on the other side; the 

 last three ai'e somewhat larger and set further apart. 

 The opercular apparatus, in accordance with the 

 shape of the head, is characterized bv its heischt. The 



like a scale. 



The greater part of the head, as well as the rest 

 of the body, is covered with a thin, silvery epidermis: 

 but the upper temporal I'egion, bet^\■een the eyes antl 

 the occiput, is naked, the surface of the bones being 

 finely grooved and granulated. 



The fins resemble in quite essential respects those 

 of the Hemibranchs and Lophobranchs. As in the said 

 fishes, the soft rays, which are thin and transparent, 

 with the tips strongly compressed in the longitudinal 

 direction of the body, show but little developed rami- 

 fication and have only scattered joints". In the sup- 

 porting apparatus of the paired fins too, we find points 

 that remind us most of the Sticklebacks. 



The true dorsal fin is obliquel}' rounded, the first 

 rays being the shortest, but gradually increasing in 

 length to the fifth or sixth, which is the longest in 

 the fin. It begins at a distance from the tip of the 

 snout measuring about half (50 — 51 %) of the length 

 of the body, and the length of its base is about equal 

 to the vertical diameter of the eye or ii little greater, 

 about 12';,, — 14 % of the length of the body. A little 

 in front of this fin ends the fin-like osseous ridge 

 formed by the projecting tips of 7* neui'al spines be- 

 longing to the abdominal vertebrtp, together with the 

 thin and transparent, feebly ossified interneural mem- 



" We are indeed ignorant of tlie manner of loconiotion employed by Argyropeleaia Olfersii; but from this strncture of the tin-rav! 

 we may conclude that the fins perform their function by means of vibrations. Tliis is the case, as we have seen above, not only in th( 

 Sticklebacks and Pipefishes but also in the Dory, where the second dorsal and the anal fius are furnished with similar rays. 

 *■ In Argyropdecas hemt'gi/mnus belonging to the 3rd— 9th vertebrae. 

 Scnndinni^iiin lushes. 117 



