14 



SALMONIDiE OF BRITAIN. 



this is a very noteworthy fact, as in some instances in which there exists a 

 discrepancy in the accounts of two authors as to the shape of this fin, such may 

 be owing, not to an error in facts, but to a difference in the method in which the 

 examination was conducted. 



when the muscles of the tail are of great 



fts. 



^^ 



■^, 



Fis- G. Caudal fm of a sea trout, expanded half aud two-thirds. 



Locomotion is the main use to which the fins of fishes are put, but even in 

 locomotion other forces arc frequently or rather generally brought iuto i)lay to 

 assist the fins, whether such is for the purpose of swimming, or for leajiing as in 

 the salmon while ascending rapids 

 assistance. 



The skeleton* or cndo- 

 skolcton of Salmonoids, 

 consists essentially of a 

 skull and a vertebral or 

 spinal column (to which 

 are certain appendages) 

 these forming a protection 

 to the cerebro-spinal ner- 

 vous system and large 

 blood-vessels present in 

 the long axis of the body. 

 The vertebra?, of which 

 the spinet is made up, 

 consist of a varying num- 

 ber of bones, the bodies of 

 each of which are excavated 



lis. 



i^^-- 



at either end causing them 

 to be bi-concave or amphi- 

 ccelous. The cavity jiro- 

 duced by the apposition of 

 the two concave surfaces is 

 filled up with gelatinous 

 substance the remains of 

 the notoohord, while it is 

 covered in by connecting 

 ligaments. Consequently, 

 between the vertebras are 

 elastic balls of semifluid 

 consistence which enables 

 them to move freely one 

 upon another. 



Fig. 7. Section of two caudal 

 vcrtebr.'c of a salmon, c. cen- 

 trum : lia, li.Tmal arch : lis. 

 ba:)mal sjune : na, neural arch : 

 jis, neural Bpine. 



' The numerals employed for the various bones in this work are almost identical with those 

 of Cuvier and Owen, being as follows: — 1, Frontal. 2, Prefontal. 3 (Ef/imoirfc, Cuv.), Nasal. 

 4, Postfrontal. 5 (Basilaiir, Cuv.), Basioccipital. 6 (.S'^i/jomlWc pr/Hc-yw^ Cuv.), Basisphenoid. 

 7, Parietal. 8 {Iiiter2>nrictal on Occipital supcricnr, Cuv.), supra-occipital. M (Occipital exteriw, 

 Cuv.), Paroccipital. 10 (Occipital lateral, Cuv.), Exoccipital. 11, Alisphenoid. 12, Mastoid. 

 13 (liochcr, Cuv.), Petrosal and Otosteal. 14, Orbitosphenoid. 15 (Sphciwiilc autcrieiir, Cuv., 

 Etliiiiiiid and Etlniivtiirhimi!, Owen), Basisphcnoid (Huxley). 16, Vomer. 17 (Inteniuixillairc, 

 Cuv.), Premaxillary. 18, Maxillary. 11) (Sous-orhilairc, Cuv.), Infraorbital ring. 20 (Nasal, Cuv.), 

 Turbinal. 22, Palatine. 23 (Tciiqmral, Cuvier, Epitympanic, Owen), Hyomandibular (Huxley). 



