J. K. Tliacher — Median and Paired Fins. 309 



EXPLANATION OF PLATES. 



The figures are all drawn with a camera, and photo-lithographed. They are all 

 three-fourths of the size of the originals, except figs. 1, 2, 3, 4, 20, 21, 22, 60; figs. 

 20, 21 and 22 are three -eighths, and 60 is a little less than twice natural size. 



Plate XLIX. 



Figure l. — Petromyzoa mariiitis. a, Ligamentum longitudinale, or ridge-pole of my- 



elonal canal ; b, notochord ; c, neural arches. 

 Figure 2. — Petromyzon marinus. a, fin -rays ; &, intermuscular septa. 

 Figure 3. — Petromyzon marinus. a, fin-ray; b, fin-muscles. 

 Figure 4. — Section of Petromyzon marinus, to show the relation of the neural arches to 



the muscular segments ; a, intermuscular septum ; &, neural arch ; c, blood-vessel ; 



d, muscular segment ; e, fatty-fibrous ridge-pole of neural canal. 

 Figures 5, 6. — Mustelus canis. First dorsal. 



Plate L. 



Figures 7-10. — Mustelus canis. First dorsal. 

 Figure 11. — Mustelus canis. Second dorsal. 



Plate LI. 



Figures 12-15. — Mustelus canis. Second dorsal. 

 Figures 16, 17. — Mitstelus canis. Anal. 



Plate LII. 



Figures 18, 19. — Mustelus canis. Anal. 

 Figure 20. — Galeocerdo tigrinus. First dorsal. 

 Figure 21. — Galeocerdo tigrinus. Second dorsal. 

 Figure 22. — Galeocerdo tigrinus. Anal. 

 Figure 23. — Eidamia Milberti. First dorsal. 



Plate LIII. 



Figure 24. — Eidamia Milberti. First dorsal. 

 Figures 25. 26. — '' " Second dorsal. 



Figures 27, 28.— " " Anal. 



Figure 29. — S-phyraa zijgcena. First dorsal. 



Plate LIV. 



Figure 30. — Sphyrna zygcena. First dorsal. 



Figure 31. — '' " Second dorsal. 



Figure 32.— ' '' Anal. 



Figures 33-35. — Eugomphodus { Odontaspis) litoralis. First dorsal. 



Plate LV. 

 Figures 36-39. — Eugomphodus litoralis. First dorsal. 

 Figures 40, 41. — " " Second dorsal. 



Plate LVT. 

 Figures 42-46. — Eugomphodus litoralis. Second dorsal. 

 Figures 47, 48.— " " Anal. 



