438 LOUIS F. DE POURTALilS. 



part of the roport : " There are some delicate shells of mollusks from 

 deptlis beyond five hundred fathoms where they were certainly living." 

 He also called attention to the existence of green sand as one of the 

 characteristic deep-sea formations of the present day. " A mixture in 

 about equal proportions of Globigerinae and black sand — probably 

 green sand." In concluding he called attention to the importance for 

 geologists of a knowledge of the habitat and distribution of Forami- 

 nifera, on account of their large share in the formation of rocks, at least 

 in the Cretaceous and Tertiary periods. 



While examining the samples of bottom collected by Commander 

 Sands, he made the discovery that many specimens of Orbulina con- 

 tained a young Globigeriua, more or less developed, so that the two 

 genera must be considered as probably two stages of alternate genera- 

 tion. He was also able, in some of the specimens collected by Com- 

 mander Sands, to trace the successive changes of the Foraminifera 

 into green sand, from the most fresh-looking Foraminifera of various 

 species until all trace of their origin was apparently lost. 



In 1858 he gave a general report of his work on the Foraminifera 

 of the bottoms collected by the various Gulf Stream expeditions up 

 to that time. This was by no means the close of his studies in tliis 

 direction, for he continued as a part of his duties of Assistant on the 

 Coast Survey to have chai-ge of the collection of bottom deposits. 

 The general results of his studies he jiublished in Petermann's " Geogra- 

 phische Mittheilungen" for 1871, with a map showing the geographical 

 and bathymetrical distribution of the different bottoms on tlie east 

 coast of the Atlantic. Fitted as he was both by taste and early train- 

 ing for zoological studies, it was natural that the Coast Survey should 

 look to him for an expansion of its biological work, and in 1867 he 

 was assigned to the Coast Survey steamer Corwin in order to make 

 Buch biological collections as would tend to elucidate the fauna of the 

 bottom of the Gulf Stream between the Florida Keys and Cuba. 

 The bi'eaking out of yellow-fever on board the steamer after a few 

 casts had been taken put a stop to all further work for that season. 

 But early in 1868 the campaign was opened again with such success, 

 Acting Master Piatt, U. S. N., commanding the Coast Survey steamer 

 Corwin, that Mr. Ponrtales induced Professor Agassiz, wiio had be- 

 come greatly interested in the extraordinary results of the second 

 expedition, to join him in the Bibb for the third cruise in 18G9. The 

 second expedition, from the brilliant results obtained, may be said to 

 have awakened general interest in the subject of the bathymetrical 

 distribution of animal life. The discovery alone of the great range in 



