208 



ZOOLOGY 



SECT. 



S.Or 



T.C 



Pa.ch. 



IIM 



Brl 



idt. 861. Skull of young Salmon, second week after hatching 

 the investing bones removed. Au. auditory capsule ; Br. 1, 

 first branchial arch ; Ch. notochord ; C. Hy. hyoid cornu ; 

 Fo. fontanelle ; G. Hy. basihyal ; H. Hy. hypohyal ; H. M- 

 hyomandibular ; 1. Hy. interhyal ; fl, I' 2 , labial cartilages ; 

 Mck. Meckel's cartilage ; M. PL metapterygoid region of 

 primary upper jaw ; Pa. ch. parachordal ; PI. Pt. palato- 

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

 region of cranium ; Sy. symplectic region of suspeusorium ; 

 T. C'r. cranial roof ; Tr. trabecula ; II, optic foramen ; V, 

 trigeminal foramen. (From Parker and Bettany's Morphology 

 of the SI- nil.) 



set of pterygiophores, so that the fin-skeleton is multiserial, as in 



the Dog-fish. The 

 proximal series con- 

 sists of slender bony 

 rays the interspin- 

 ons bones (Fig. 862, 

 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 

 myonieres of the 

 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- 



lage (pig. o] forming the third series of radials. The dermal fin- 



rays or Icpidotrichia (D.F.R.), which lie in 



the substance of the fin itself, are slender 



bones, jointed like the antennas of an Arthro- 



pod, and mostly branched in the sagittal 



plane (Fig. 865, D.F.E.). 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 cartilaginous 



nodules (ptg.3). In the caudal fin (Fig. 858) 



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



on the broad haemal arches of the posterior 



caudal vertebrae. The second dorsal or adi- 



pose fin has no bony support. 



The shoulder-girdle (Fig. 863), like the 



skull, consists of a primary shoulder -girdle, 



homologous with that of a Dog-fish, and of 



several investing bones. The primary shoulder- 



. Y. -ri- i / i r v 



girdle in the young Fish is formed of dis- 

 tinct right and left bars of cartilage, which 

 do not unite with one another ventrally. In 

 the adult each bar is ossified by three bones, 

 a scapula (SCP.), situated dorsally to the 



DF.R 



FIG. 8<>2. Salmo fano. 



A dsrmai fin-ray with its 





