64 APPENDIX TO KEPORT OF THE SECRETARY. 



water that occupied the whole saline region during (as it would appear) a glacial 

 period. 



Lastly, curious information was obtained respecting the ages of not only the big 

 trees of California, but of equally aged pines and junipers, which are proofs of that 

 duration of existing conditions of climate for which evidence has hitherto been sought 

 rather among fossil than among living organisms. 



Zoology. — Prof. Joseph Leidy, the eminent comparative anatomist and 

 microscopist, made his second visit to the West the past season under 

 the auspices of the Survey. He made a careful exploration of the coun- 

 try about Fort Bridger, Uinta Mountains, and the Salt Lake Basin, in 

 search of rhizopods. He has been engaged for a long time on a memoir 

 on this subject, which will eventually form one of the series of the quarto 

 Eeports of the Survey. 



The rhizopods are the lowest and simplest forms of animals, mostly 

 minute, and requiring high power of the microscope to distinguish their 

 structure. While most of them construct shells of great beauty and 

 variety, their soft part consists of a jelly-like substance. This the ani- 

 mal has the power of extending in threads or finger-like processes, which 

 are used as organs of locomotion and prehension, often branching. 

 From the appearance of their temporary organs, resembling roots, the 

 class of animals has received its name of rhizopoda, meaning literally 

 root-footed. 



In compensation for the smallness of these creatures, they make up 

 in numbers, and it is questionable whether any other class of animals 

 exceeds them in importance in the economy of nature. Geological evi- 

 dence shows that they were the starting-point of animal life in time, and 

 their agency in rock-making has not been exceeded by later higher and 

 more visible forms. 



With the marine kind, known as foraminifera, we have been longest 

 familiar. Their beautiful many-chambered shells — for the most part 

 just visible to the naked eye — form a large portion of the ocean-mud 

 and the sands of the ocean-shore. Shells of foraminifera likewise form 

 the basis of miles of strata of limestone, such as the chalk of England 

 and the limestones of which Paris and the pyramids of Egypt are built. 



Fresh-water rhizopods, though not so abundant as marine forms, "are 

 nevertheless very numerous. They mainly inhabit our lakes, ponds, and 

 standing waters, but they also swarm in sphagnous swamps and ever 

 live in newest earth. Professor Leidy has devoted several years of 

 etudy to the fresh- water rhizopods of the eastern portion of our country, 

 and his especial object in the past expedition was to investigate those 

 which are to be found in the elevated regions of the Rocky Mountains. 



Dr. Elliott Cones, secretary and naturalist of the Survey, though pre- 

 vented from taking the field during 1877 by the press of publications, 

 which required his stay at the Washington office, has continued his in- 

 vestigations in Mammalogy and Ornithology. The printingof the " Birds 

 of the Colorado Basin" has steadily progressed during the year, and very 

 great accessions of material for his forthcoming Eeport -oh North Ameri- 



