1891-92-] Dragon- Flies : their Life- History. 15 



Among fossil insects dragon-flies are said to hold a promi- 

 nent position, and their remains appear to be numerous. In 

 Britain they have been found more especially in the Purbeck 

 Beds of Swanage and the vales of Wardour and Aylesbury, 

 &c. ; but the richest strata are those of the Upper Miocene at 

 CEningen, in the Rhine Valley, the Middle Miocene at Badaboj, 

 in Croatia, and more especially the celebrated limestone long 

 quarried for the light - yellow porous lithographic stone at 

 Solenhofen, near Munich. The excessive fineness of grain 

 of this last deposit has enabled it to preserve in the most 

 marvellous perfection abundant remains of animal life, both 

 of sea and land. It is said to be of marine origin, although 

 this is doubted. The remains of gigantic dragon-flies found 

 in it are numerous and perfect, even to the lace- work of their 

 wings. But it is remarkable that no traces of their larval 

 condition have been found, although discovered in most of 

 the other strata ; hence the insects have been regarded as 

 having been drowned in the sea or a lake and washed ashore. 



List of Microscopic Slides prepared by the Author to 

 Illustrate the above Paper. 



1. Mask of larva, 1st type. 



2. ,, „ 2d „ 



3. n 11 3d 11 



4. Head and mask of larva. 



5. Respiratory canal and spinous processes. 



6. 11 11 



7. Gizzard of larva. 



8. 11 11 



9. Tracheal tubes and Malpighian bodies. 



10. Antennte of larva. 



11. Gill leaf- plates of larva, Agrionidse. 



12. Immature wings n n 



13. Compound eye of Aeschna. 



14. Ocelli (simple eyes) 11 



15. Mouth-organs n 



16. Spiracles n 



17. Forelegs n 



18. 11 Agrion. 



19. Wing, Aeschna. 



20. 11 Agrion puella. 



21. 11 11 minium. 



22. Reproductive organs and " claspers," male. 



