NiCKERSON. — Scales of Lepidosteus. 



PLATE II. 



Fig. 10. Section tlirough tlie axis of a spine papilla in which secretion has begun. 



From fish 150 mm. long. X 387. 

 " 11. Optical section of spine broken off from scale of a young Lepidosteus 



300 mm. long. X 387. 

 " 12. Tip of spine loosened by use of caustic potash , a, before treating with 



hydrochloric acid; b, after applying acid. X 137. 

 " 13. Section through posterior edge of a scale from a fish 300 mm. long (52 



months old), showing portions of imbedded bases of four spines. X 200. 

 " 14. Base of a lost (resorbed ?) spine, which had been surrounded by ganoin 



before the latter was destroyed by decalcification. From fish 460 mm. 



long. X 198. 

 " 15. Section (prepared by grinding) through scale of fish 300 mm. long, from 



S P Bartlett. X 31 

 " 16. Section through posterior margin of decalcified scale from fish 300 mm. 



long. X 198. 



