88 



COMPARATIVE ANATOMY. 



Sit' 



Fio. 69. PECTORAL ARCH AND FIN OF Hcptanchus. 



XL', SB 1 , pectoral arch, with a nerve-aperture at NL ; Pr, J/.y, 1/7, the tliree 

 basal elements of the fin pro-, meso-, and metapterygium ; Ea, cartilaginous 

 fin-rays ; a, b, the main fin-ray, lying in the axis of the metapterygium ; 

 +, single ray on the other side of the axis (indication of a bi.senal type) ; FS, 

 horny rays, cut through. 



,,z 



CotCf) 



Fi<;. /<.- -I,r.i-r PECTOEAl AJJCH AND FIN OF Tin: TROUT. r'nn>i the outer side. ) 



/'. /'', Z? 3 , chain of secondary bones of the pectoral arch, (clavicle and supraclavicle), 



wliicli is (.iiiiicrtnl \\iili tlii- skull by mraiis of ihr post-temporal ' '/// ; .v iind 



Co(<.'h, IPCIIIV M-;i]iiil,'i and curacoid, which havi- bccdin.- dry, ],.] d in tin' rartilag.- 



A'.( ; /., loraiiifii in scapula ; J/ 1 . mct:i]iti ry^iuni : A'", J!n, tlic MT.md and 



third, and 4, tin 1 fourth basal rlrninit ui' ilir tin ; A'./ 1 , the second cartilaginous 



low (if radii ; IIS, bmiy ray OD I In- bi>rd<T of t lir I'm, \\hirh is cdiiiKvird with the 

 fourth basal element ; /', S, bony fin-rays, shown cut away from th. iruttaohmonls. 



