COMrAUATIVE STUDY OF SCOMISUOID FLSIIEH 35i 



tliLs ligtüucut iiudov tlu; luiiiiii! of tlic cluvii'ubir lifi;iiiu(iiit. It is iusoiitxl to tlH3 

 iuner side of tlio supriu'lnviclo nt oiu; oui], mid to this <x,'cipitfil region or to 

 Olio of tho !iut»n-R)r voitcI)nu! at the otiior. Auothcr ligament, commoulj' foiuid 

 iu the tcleosteaii fishes is Joup, situated iu the spiual caual, above the spiiud 

 colli, thus coiuicotiufj; the veitebnu;. A short iiiediiui h'}»nm(;nt oouuectiujij tho 

 skill iu the heiul to the ft'oiifcils is pn-uliar t<.) the Tluuuiidao. A pjiir of 

 tliiii aud short ligiuueiits is found liotwcon tho fii'st and second veitebriu; iu tlio 

 genus Awns. Besides these there me luanj- ligaments connecting diflei-out 

 puts of the skeleton. 



Tendons ai-e \\i\\ developed noai' both ends of the body, especially uoiir 

 the tail, aud iu tlie fishes of the Katiiwonicbio. A longitudiual tendon running 

 from the tail aud formiug the axis of a large muscular cone is very long in 

 Auxis (fig. 2). Til this genas two tendons formiug the anteiior esti'emities of 

 the two hjio'i'^i'^l ooiies of mj-otomes just Ixilow the median septum between 

 tlie eiiasial and hj-^iaxial portions of the lateral muscle are remarkable. Tho 

 exteiouil tendon is atbiched to the supraclavicle, just behiud the attaclmient of 

 the clavicular ligament, jmd the iutonial to tlio large lateral tubercle of the 

 second vertebra. Between ever^- tw( > Ixxly-segmeuts we find a pair of tendons. 

 Tlitso tendons connect the intermusculiir bones, and are joined at the abaxial end 

 to the myocommata. Iu tlio teleostean fishes these tendons are simple, but in 

 the plecostean fishes they are longer and much more complicated, as they 

 make more acute angles with the vertebral columu. 



NERVOUS SYSTEM AJSTD SENSE ORGANS. 



The brain-cavit}- of thtj scombroid fishes is small as iu other teleo- 

 stomatous fisli&s, and the brain does not occupy even tlie whole of this small 

 cavity, Ixjing sumnmded by a tliick layer of a fiitty substance. Thus even a 

 tunny of ca 40 kg has a brain as small tis a miin's thumb. The brain of tho 

 scombroid fishes does not difler much from tlie common type of the brain of 

 the Teleostomi. The enormous development of the optical lobe and cerelxillum 

 is stiikiug. The nondevelopment of the cerebral hemisphei'e is also remarkable. 

 In the Plecostei the optical lobe has a very large groove on the venh-al side, 

 as if tho lolie is made by folding, when seen from that side. The groove is 

 csixjcially remarkalile iu Auxis, in which a coiTesixjuding groove is foimd in the 



