208 



ZOOLOGY 



SECT. 



set of pterygiophores, so that the 



S.Or 



fiu-skeletuu is multiserial, as iu 

 the Doa-fisli. The 

 proximal series con- 

 sists of slender bony 

 rays — the intcr-spin- 

 ous hones (Fig. (SG2, 

 PTG. 1 ; Fig. 865, 

 PTG.), lying in the 

 median plane, be- 

 tween the muscles 

 of the right and 

 left sides, and more 

 numerous than the 

 myomeres of tlie 

 regions in which 

 they occur. Their 

 distal ends are 

 broadened, and with 

 them are connected 

 the second series 

 (PTG. 2) in the form 

 of small dice-box 

 shaped bones ; to these, finally, are attached small nodules of carti- 



10. 861.— Skull of young Salmon, sucoiid week aftei- hatching ' 

 the investing bones removed. Ai'.. auditory capsule ; Bi-. 1, 

 first branchial arch ; Ck. iKjtochord ; C. llv. hyoid cornu ; 

 Fo. fontanelle ; G. H>i. li.-isihyal ; H. ////. hypohyal ; //. M- 

 hyoiiiandiliular ; 1. Hy. interhyal ; /i, 1-, labial cartilages ; 

 Mck. Meckel's cartilage ; M. Pt. nietapterygoid region of 

 primary upper jaw; Po,. ch. parachordal; PL Pt. palato- 

 pterygoid region ; Qu. quadrate region ; S. Or. supraorbital 

 region of craiuum ; .S//. symplectic region of suspensorium ; 

 T. Cr. cranial roof; Tr. trabecula ; II, optic foramen; V, 

 trigeminal foramen. (From Parker and Bettany's Morphology 

 of the S>:ull.) 



lage (2^tg. 3) forming the third series of radials. 

 roys or Jeijidotrichia {D.F.R), which lie in 

 the substance of the fin itself, are slender 

 bones, jointed like the antennae of an Arthro- 

 pod, and mostly branched in the sagittal 

 plane (Fig. 865, D.F.R.). Each is formed of 

 distinct right and left pieces (Fig. 862), in 

 close contact for the most part, but diverging 

 below to form a forked and dilated end, 

 which fits over one of the cartilacjinous 

 nodules {ptg.S). In the caudal fin (Fig. 858) 

 the dermal rays (D.F.B.) are similarly seated 

 on the broad hiemal arches of the posterior 

 caudal vertebra?. The second dorsal or adi- 

 pose fin has no bony support. 



The shntldcr-girdlc (Fig. 863), like the 

 skull, consists of a 'primanj shoidder-girdlc, 

 homologous with th?t of a Dog-fish, and of 

 several investing bones. The primary shoulder- 

 girdle in the young Fish is formed of dis- 

 tinct right and left bars of cartilage, which 

 do not unite Avith one another ventrally. In 

 the adult each bar is ossified by three bones, 

 a sccqnda. (sc?.), situated dorsally to the 



The dermal fin- 



UF.R 



PTG.1 



Fi(i. 8ii2.— Salmo fario. 



A dermal fin-ray with its 

 supports. IKF.Ji. dermal 

 fin-ray; PTG. 1, jiroximal 

 pterj-giophore (interspin- 

 ous bone); PTG -. middle 

 pterygiophore; ptii. S, dis- 

 tal pterygiophore (cartila- 

 ginous). 



