EXPLANATION OF PLATE V. 



Fig. 1. Caudal skeleton of Coccosteus, after Pander ; ep and hy, epural and hypural 

 elements, all of which do not bear rays, but, as in Pterichthys, extended 

 out only as far as the scaly covering of the tail ; d dorsal, a anal fins. 



Fig. 2. Caudal skeleton of Polypterus, from Agassiz's Poissons Fossile, modified after 

 Kolliker; ep' , styliform ray-bearing and nodular non-ray-bearing interspi- 

 noiis epural elements ; ep, neural spines ; hy, hypural ray-bearing elements. 



Fig. 3. Caudal skeleton of adult Lepidosteus, from Kolliker, showing the urochord 

 more prolonged and attenuated than in the preceding. 



Fig. 4, Caudal fin of Platysomus as restored by Agassiz in the Poissons Fossile; ep 

 and hy, epural anil hypural pieces ; u, urochordal end of the skeletal axis, 

 V hich was mainly notochordal. 



Fig. 5. Tail of a young specimen of Lepidosteus, 11 centimeters long, from Balfour and 

 Parker ; cd, permanent caudal ; ff, eradiate fin-fold of opisthure ; op, opis- 

 thure ; my, my, its myotomes. 



Fig. 6. Side view of the tail of a larva of Lepidosteus, 21 millimeters long, dissected 

 and magnified so as to show its structure at this stage ; ep and hy, epural 

 and hypural cartilaginous rudiments of the neural and haemal arches ; ch, 

 chorda ; ch , its opisthural portion, which afterwards becomes partially aborted 

 and included in the upper part of the tail ; cd, tip of fold, which becomes the 

 permanent caudal ; oj), opisthural lobe of the larval tail ; ff, lophocercal fin- 

 Ibld, which contains horn-fibers hf throughout its extent. After Balfour 

 and Parker. 



Fig. 7. Magnified view of the caudal skeleton of a young Cyprinodont (Gambusia), i 

 of an inch long, and which was removed from the ovarian follicle in which it 

 developed ; ch, chorda ; ep and hy, epural and hypural cartilages ; ms, me- 

 dulla spinalis ; r r r, rays. 



Fig. 8. Caudal skeleton of Centrina salviani ; ep and hy as before ; va, vertebral axis ; 

 ff,ff, its dorsal and ventral membranous lobes, which include numerous 

 horny and partly osseous supporting fibers. From Giinther. 



114 1094 



