516 



CENOZOIC ERA— AGE OF MAMMALS. 



wonderful instincts, and organized social habits, have been developed 

 together since the introduction of this order in Early Tertiary. 



In the fresh- water Miocene of Auvergne, France, there is a remark- 

 able stratum called indusial limestone, because it is largely composed 

 of the cast-off hollow cases (indusia) of the caddis- worm or larva of the 

 caddis-fly (Phryganea), cemented together by carbonate of lime. The 

 number of these cases is countless. The caddis-worm of the present 

 day forms for itself a hollow cylindrical case, of bits of stick or pieces 

 of shell, or sometimes of whole small shells, binding these together by 

 means of a kind of web. In this hollow cylinder it lives, only putting 

 out the head and two or three first joints of the body, to which the 

 feet are attached, in walking. When they complete their metamor- 

 phoses, they leave 

 their cases. Fig. 

 881 is a recent cad- 

 dis-worm with its 

 case of small shells 

 stuck together ; 

 Fig. 880 are indu- 

 sia of the Miocene 

 caddis-worm ; and 

 Fig. 879 is the 

 limestone in place, 

 a being the indusial 

 layer. 



In Auvergne, in 

 Miocene times, 

 there existed a shal- 

 low lake, in which 

 carbonate of lime 

 was depositing, as 

 in many lakes of 

 the present day. In 

 this lake lived myr- 

 iads of caddis- 

 worms, and their 

 indusia accumula- 

 ted for countless 

 generations. 



In the Tertiary 



strata, about the shores of the Baltic, and also in Sicily, in Asia Minor, 

 and several other localities usually associated with lignite, are found 

 masses of amber. This substance is a fossil resin of several species of 

 Conifer, especially Pinites snccinifer. It is often quite transparent, 



Fig. 881. 



Figs. 879-8S1. — 879. Indusial Limestone interstratified with Fresh- 

 Water Marls. 880. A Portion (natural size) showing the Phry- 

 ganea Cases. 881. Eecent Larva of a Phryganea, with its Case. 



