(i!)-i 



SCAXIllNAVIAN risili;: 



tic bones, wliich arc altaclicd to the anterior end of 

 tlic air-l)la(l(lcr. Several cii'cunistances, of wliich we 

 siiall give an account helow, seem, hoAvever, to assign to 

 the Weberian apparatus its most important function as 

 a barometrical apjiaratus for the tish. As in tlie i'^ilc- 

 lislies, \ve sometimes liiid here that the aii'-bJadder is 

 connected with tlie skin in the scapular region on each 

 side of the body; and this is effected either immediately, 

 by means of lateral ])rocesses from the bladder, or h\ 

 a ligamentous coiniexion between the skin or the first 

 lateral ])late and the acoustic Ijone that coalesces with 

 the ail-bladder. 



In the same parts of the body, the sides of the 

 scajjular region Ijehind the clavicles, we find in some 

 (ilanomorphs {I'lotfisKs. Maldjitrninis") special ca\'ities, 

 one on each side of the body, more or less completely 

 closed bulbs of the abdominal cavity (secondary abdo- 

 minal cavities), in which a part of the liver and (on the 

 right side) the gall-bladder or a portion of the kidneys 

 ma\' tind room. In several Glaiiomorphs (Doras, Ariiis, 

 Asprcdo, Sihinis etc.) we meet with a singular sac be- 

 neath the skill behind each of tlie clavicles, usually 

 opening into a ln)lc (panis lofvrnl/s 1. jirctor((]is) at the 

 upper angle oi the pect(.)ral fin, somewhat above or a 

 little beliiiid it. W'e have already remarked a similar 

 cavity in the case of the Batrachoids (Part I, p. 133). 

 It has been interpreted as a saccate poison-gland; but 

 in neither case has its signitication been yet explained. 

 In our Sheatfisli the ]>ore leads upwards to the cavity 

 under the flat, backward process from the posterior 

 corner of the angular cla\iclc. 



These fishes are known in English as (Aitfishes on 

 account of their long and sometimes numerous barbels, 

 sensoi'v threads (corresponding to whiskers) round the 

 mouth. These barbels, accompanied sometimes by large 



labial flajis, are b\- their extraordinary develo])iiK'iit 

 esiiecialh- characteristic of the (ilanomorphs. 



The variety of form among the Glanomorphs (Xe- 

 matognates) is fairly great. About 6()0 species have 

 been described, and Ulkkkkk has distril)uted them among 

 185 genera, arranged in li families. The form of the 

 Ijod'V' varies from the ordinary piscine form, usually 

 \vith flatteiied head and well-separated caudal fin, to the 

 Anguilliform type, with the yertical tins continuous 

 round the ti]) of the tail. The plated (ilanomorphs, as 

 C(_iPi: has remarked, jjreseiit in their arninur an obvious 

 resemblance to the Sturgeons, tn Avhicli the (ilanomorphs 

 possess another likeness in the barbels on the jaws. That 

 the reseral)lance between these two groups of fishes is 

 not merely external, has l)een already shown b\- I'ah- 

 KKi;'' in his account of the analogy between the different 

 parts of the scapular arch in the armoured Glanomorph 

 CaUichtJii/s and in a Sturgeon, with /lostfemporale, sitpra- 

 cJaricida, clailcitla and iiifeiclariiiihi e(|ually distinct as 

 dermal growths. Thus the Cilanomorphs — in the ma- 

 jority of which, however, the structure of the sca}iular 

 arch reminds us most strongly of the Carps — rank as 

 the most distinct intermediate fV)rms in this respect 

 between the Sturgeons and the Teleosts. 



Most of the Glanomorphs belong to fresh water, 

 especially to the lakes and rivers of the Tropics, with 

 their deltas and brackish water; but many live in the 

 sea, whei'e the\' keep, however, to the littoral region. 

 To the natives, especially within the Tropics, these fishes 

 are in many localities of great economical value; but 

 they are generally despised by Europeans on account of 

 their repulsive appearance. ]\lany of them too, especially 

 in the tropical regions, are dreaded for their formidable 

 spines, \vliich are said to be poisonous, though as yet 

 we have no trustworthy evidence on this head. 



•I 



Fam. silurid^. 



Bodii iKilii'd (/ritlidiit pid/fs ou fhr sides): hctid also covered iritJi skin. Oidii one (ifai/i/) dorsal fin furnished iriili raifs. 

 short and situated on the abdominal part of the l/odi/. Caudal part of the bod// and tlie amd fin long. Branchial 

 arches simple (irithoiit appendicular branchia'). (HU-openings large: hranchiostegal membranes free from the isthmus. 



Thus defined, tlie famih' of the Sheattishes corre- \ — as well as to his Saeeobranehifirmes, with the'iv sm- 



sponds to Bleekeu s subfamilies Sihirifornies and Aili/e- gular. tubular, respiratory cavity along each side of 



formes — the former without, the latti'r with a small the body, and contains al)out 50 known species from 



adipose fin on the posterior part of the dorsal margin the ( >ld World and the Sunda Islands. In Glxthkh 



" Cuv., V.M,., ///.s?. Nul. I'iiiff., vol. XV, pj). 415 aiitl 52.5 ami HvnTi., 1. c, p. 302. 

 ' <Sliouldei-i/irdh: and Sternum (Ray Soc. 18G7), p. 2.^.. 



