chap. xi. St. Fd Bajada, 3 3 3 



so that even one of the great molar teeth fell into 

 pieces in my hand. We here see that the Pampean 

 deposit contains mammiferous remains close. to its base. 

 On the banks of the Carcarana, a few miles distant, the 

 lowest bed visible was pale Pampean mud, with masses 

 of tosca-rock, in one of which I found a much decayed 

 tooth of the Mastodon : above this bed, there was a 

 thin layer almost composed of small concretions of 

 white tosca, out of which I extracted a well preserved, 

 but slightly broken tooth of Toxodon Platensis : above 

 this there was an unusual bed of very soft impure sand- 

 stone. In this neighbourhood I noticed many single 

 embedded bones, and I heard of others having been 

 found in so perfect a state that they were long used as 

 gate-posts : the Jesuit Falkner found here the dermal 

 armour of some gigantic E dental quadruped. 



In some of the red mud scraped from a tooth of 

 one of the mastodons at G orodona, Professor Ehrenberg 

 finds seven Polygastrica and thirteen Phytolitharia, 1 all 

 of them, I believe, with two exceptions, already known 

 species. Of these twenty, the preponderating number 

 are of fresh-water origin ; only two species of Coscino- 

 discus and a Spongolithis show the direct influence of 



1 ' Monatsberichten der konig. Akad. zu Berlin,' April, 1845. The 

 list consists of : — 



Polygastrica. 



Campylodiscus clypeus. f Grallionella granulata. 



Coscinodiscus subtilis. 

 al. sp. 



Himantidiurn gracile. 

 Pinnularia borealis. 



Eunotia. 



Phytolitharia. 



Lithasteriscus tuberculatus. 

 Lithodontium bursa. 



„ furcatum. 



„ rostratum. 



Litkostylidium Amphiodon. 

 Clep- 

 sammidium. 



Lithostylidium Hamus. 



„ polyedrum. 



,, quadrat urn. 



w rude. 



„ Serra. 



,, uniden- 

 tatum. 

 Spongolithis Fustis. 



