626 ox THE CAUDAL FIX OF TUE TELEOSTOMI. [^V^'- ^7 



Fig. 2. Caudal fin of Aciptmser sturio. lUustratinjr tlie Ganoid lictprocercal fonu. 

 The pvoxiinal ends of the fulcra and deiniotrichia have been cut away to 

 expose the enil<)>keletal supports. 



3. Caudal tin of I'lilt/ndon xpatula. Illustrating a more ."specialized hctero- 



cercal (ianoiil caudal. As in the preceding t.vpes, the proximal ends of 

 the derinotri.hia and fulcra have been reninved. 



4. Caudal fin of Amia calm. Modified from Kolliker. Illustrating a highly 



specialized heterocercal form : usually referred to as henii-heterocercal. 

 o. Caudal fin of Cliijiea pihhardus. Illustrating a lowly specialized homo- 

 cereal caudal. 



6. Caudal tin of Notnpterns hnrneensis. On the ventral side the caudal is 



continuous with the anal tin. 



7. Caudal fin of I'lutosus sp. ? Ih-awn from a youno; specimen li inches 



(3'8 cm.) in length. The tin-rays (rf<»r.) on the dorsal side illustrate the 

 *■ procurreiit caudal " of Regan. Note that the first fin-ray anterior to 

 the hypiiral of the penultimate vertebra has no radial as a support, and 

 thus seems to anticipate a similar condition ventrally as is found 

 dorsally. 



8. Caudal tin of Siniodontis scJiall. The fusion of mdials and arches clearly 



shown. 



Plate XLVIII. 



I'ig. 9. Caudal fin of Lepfocephahis brerirosfris. 



10. Caudal fin of Angnilla vulqariii, 4j inches (12 cm.) in length. Of the 



10 rays which are trulv caudal, 6 are bifurcated distally. Note the 

 excellent evidence of fusion of radial with hamal spine shown in the first 

 hypural, the fusion line being very distinct. 



11. Ciiudal fin of Ayif/viUa vulgtiris, adult. The nrostyle and last centrum 



have completely coale.'^ced with the last hypural. 



12. Caudal tin of dinger ntlgaris. The figure was drawn from a specimen 



cleared in .xybd, thus showing the outline of the last vertebra (/.r.), 

 which otherwise lemains invisible. The first and secinid hypurals show 

 the fusion of radial and arch extremely well. The dermotrichia are cut 

 .short. 



13. Caudal fin of Myrns rnlgarin. Cleared in xylol. 



14. Caudal tin oi Ficrasfer (Kchiodon) dentatus. From Emery. Illustrates 



extreme condition of geph\ rocercy. A distinct gap can be seen in the 

 median line separating the dorsal and ventral dermotrichia. 



15. Caudal fin of Syngnatlivs acus. Illustrates an e.\tremely simple type of 



homocercy, very symmetrical in ajipcarance, though really wholly 

 hypa.xial. 



FlATB XLIX. 



Fig. Ifi. Caudal fin of Ammndgies tohianns. 



17. Caudal tin of Moh-a vulgaris. 'J'he dorsal caudal radials (d.c.r.) are r|uite 



free, but sliglitly overlap the neural arch of the penultimate vertebra, 

 thus giving, in the figure, the appearance of fusion. 



18. Caudal fin of Gudiruhis argenfalns. One of the best instances among 



Teleostei of the formation of hypurals and epurals by the coalescence of 

 nidials and arches; radials are to 1)8 seen in the various stages of fusion. 



19. Caudal fin oi' Scrrmius cahrilla. A somewhat loosely constructed skeleton 



and a type of homocercy frequently met with among the Acanthopterygii. 



20. Caudal fin of Bn.r salpa. Figured from a specimen 4 cm. long. The 



young stage has been chosen on account of the neural arch ot the pen- 

 ultimate vertebra being separate from the dorsal caudal radial immediately 

 posterior to it : these two elements fuse in the adult condition; otherwise 

 the adult form is the .same. 



21. Caudal fin of La/n-us ffxlivii.t. The figure gives the appearance after 



clearing with xylol. 



22. Caudal fin of Scomber scomber. Figured as seen afttr clearing agents were 



used ; no.e tht; last ceiitnim shows no sign of upturning at its posterior 

 end. 



23. Caudal fin of Zcus/aber. 



2I-. Caudal fin of .Soico liitci. As it appears when cleared in vybd. Note 

 the spinal cord pierces the lu'unil arch of the lust centrum. 



