KI.ASMdliliANCUS. 



1073 



or, MS ill the llaxs (tiu'. ;i()0, nt/it), l)y :i iiioir cxti'ti- 

 sivc cai'tiliijiX'. strctcliiim' rnuii the Idwcr |i:ir1 tA' the 

 hyoiuiiiidiliiiliir Ihiik.' to the iioslorliilal region. ( )iitsi(lc 

 this |)linr\ii,i;(':il and masticatory aiiparatiis tlicri.' lie as 

 a rule three (sdiiietimes — as in several SharisS [tig. 

 29<S, Inis and lnii\ — miiy two, sometimes — as in the 

 Rays — none) i>airs of laliial eartilaues, the two largest 

 mid most con-itaiit meetiiiii- at each corner of tlie mouth. 

 Where tlie\ are all present, two of tliem {Ims) lie, one 

 hefore and below the other, on the outside of the palatu- 

 <iuadrate cartilaue. the third {h)ii) outside the Meckeiian 

 cartilaiie. 'I'he former two answer to the intermaxil- 

 laries and maxillaries, the latter is homologous with 

 the maiidilile. 



The position occupied in relation to the said ske- 

 letal parts li\- these cartilages recurs in a number of 

 cartilaginous rods (tig. 298, ers). first described by 

 Hatiikk", which lie in the skin between the gill-open- 

 ings, forming the outer suijport of the above-mentioned 

 cartilaginous rods in the branchiostegal memliranes (fig. 

 298, //)•). (iKcKM'.An;' called the first-mentioned rods 

 outer (/ill-drclics, and considered them, as (Yviki; had 

 partly done', to be vestiges of the more complex 

 branchial arches of the Marsipobranchs. Parker'' called 

 them crfrarisccrals or e.rfrahranch'uils, and saw in them 

 ■ hoimdogues of the shoulder-girdle (the scapuhe and 

 coracoid bones), as being extracostal growths. \ATiere 

 their development is highest, as in the majority of the 

 Sharks, thev consist of two parts, a dorsal and a ventral, 

 which meet and are applied to each other throughout 

 a greater or less portion of their extent. In several 

 Sharks and in the Rays they either are rudimentary, or 

 have only the ventral parts developed (fig. 298), or are 

 eiitireh- absent. Tlie angular, hooked or forked venti-al 

 ends of these "outer gill-arches" are joined below, from 

 one side of the body. to the other, by an horizontally 

 set, filirous membrane; and in this manner is formed, 

 under the hvpobraiiehial (lowest, figs. 298 and :Wi). Iihr) 

 I and eopular (hhr) parts of the true branchial arches, a 

 special ehaiidier, a prolongation of the pericardial cavity, 

 to receive the heart with the conus arteriofiKS and, 

 within an anterior division, the truncus arteriosKS. 



The hyoid arch shows an entirely different com- 

 position and suspension in the Sharks and Chima'ras 

 on the one iiaiid and in the Rays on the other. In 

 the former the true middle part {leratohi/oideuni, figs. 

 29 I and 298, clii/) is suspended from the lower ex- 

 tremit\- of the Inomaiidibular cartilage [lini), and the.se 

 parts are united below, from one side of the body to 

 the other, by the lirst copula {hosilii/oidciim, bhfi). In 

 the l!a\s the hyoid arch consists on each side, as a 

 rule, of ;^> or 4 jiarts, the lowest {hijpohyoideum, fig. 

 ;-500, ///;//), as well as the lowest part of the first branchial 

 arch {lii/jKihrdHrliiali'), meeting the first copula {hlii\). 

 Among the remaining parts of the hyoid arch the 

 ceratohyoid {'■lii/) and e|)ihyoid {elii/) are the most con- 

 stant; the uppermost jmrt (sthy), answering to the sty- 

 lohyoid of the Teleosts, is either cartilaginous or re- 

 presented ]>\ a ligament, and suspends the arch from 

 the upper posterior angle of the hyomandibular cartilage. 

 The true branchial arches consist as a rule of four 

 parts on each side — the hyijobranchial (hbr), the cera- 

 tobranchial {cbr), the epibranchial (cbr), and the pha- 

 ryngobranchial (phbr). R)Ut between the lowest parts 

 (the hypobranchials) there appear in the Sharks, though 

 their occurrence is irregular, unpaired pieces (copular 

 parts), sometimes five in number. Only the hindmost 

 and largest (bbr), under which tlie heart is situated, 

 is constant, and tiiis is always present in the Rays 

 as well, where it attains a still greater development. 



GDI-rakers are usuall}' wanting in the Elasmo- 

 branchs; but two remarkable exceptions are formed by 

 the largest Sharks known, the North Atlantic Basking 

 Shark and the Whale-Shark {Bhinodon fi/piciis) of the 

 Cape of Good Hope and the Indian Ocean east of Africa. 

 Like the whales, these Sharks live on small animals, and 

 like the Teleosts that feed in the same way, they are 

 furnished with a tiltering apparatus ("gill-grating'\ 

 Steenstrui% .see fig. 832, ]>. 1 14.")), which separates the 

 food fi-om the water that [Hnirs from the mouth at 

 the same time and linds an outlet through the gill- 

 slits. This tiltering ajijiaratiis is composed in the Bask- 

 ing Shark' of fine, setiform, and den.se gill-i-akers, up 

 to (i inches long, the raicro.scopical structure of which 



" Anat. Phil. Loiters. Kiemenapp., Zungenh. Wirbellb. (18,S2), p. 83. 

 ' Unters. Vergl. Anat. Wirketth., 3:tes Heft, p. 1G4. 

 "■ Lemons, ed. 2, torn. VII. p. 307. 

 '' Trans. Zool. Soc. Loud., vol. X. p. 212. 



' (iu.NNERUS, Trondhj. Selsk. Skr., pari. Ill (ITfi.")). p. 4i;: Foii.is, I'n. 

 Vid Selsk. Forh. 1873. Xc 1. p. 47. tab. II. 



Bosl. Sw. Xat. Hist. 18.54. p. 203: Steenstp... Overs. D. 



