Stodder.] 76 [November 7, 



seventy miles south of Paita, Peru. Dr. Winslow describes the local- 

 ity as a plain about fifteen miles from the sea, and separated from 

 the coast by a range of hills of slate rocks four to six hundred feet 

 hio-h. Within the plain, and near the base of the hills, is an extensive 

 depression about two hundred feet deep, with nearly vertical walls ; 

 his opinion being that the depressed part has subsided from the gen- 

 eral level of the plain. He estimated the surface of the depressed 

 portion to be about the sea level, or possibly lower. The surface was 

 covered by salt. He considers that the whole plain has been covered 

 by the sea in recent geological times, but whether there is any open- 

 ing through the hills by which the sea could have obtained access, he did 

 not say. The earth was taken from a stratum two to four feet thick, 

 cropping out of the walls of the depression described, about fifteen 

 feet below the level of the plain. The superincumbent strata con- 

 tain recent shells, bones of cetacea and pebbles, followed by one to 

 two feet of yellow sand, and then the deposit from which the speci- 

 men was taken. All the fossils being recent, according to Dr. Win- 

 slow, the deposit may be considered as Post-tertiary. 



The earth somewhat resembles earths from Monterey, California. 

 It is of a light yellowish color, and rather firm consistency ; it crum- 

 bles to a coarse powder on the application of a little force, but the 

 component organisms of the powder are cemented so firmly, that it 

 is very difficult to reduce it to its ultimate constituents. It is almost 

 all organic, the quantity of sand being but a small percentage, with 

 barely enough lime to produce a slight eflfervesence with acids. 



Mr. C. G. Bush has cooperated with me in the examination of the 

 organisms, and a large proportion of the species to be named were 

 found only by him. 



The microscopic organisms are RMzopoda and Diatomacece. 



Rhizopoda. 



Tlie Polycistince are moderately abundant, but nearly all only fi-ag- 

 ments, which would not afford specific characters, even if there were 

 any reliable authority for classifying them. 



The Dictyocha are represented by several of Ehrenberg's species. 

 They were placed by Ehrenberg in his heterogeneous group of Poly- 

 gastric Infusoria, and with, or near to, the Diatomacece ; other 

 naturalists have been unable to see any affinity to the Diatomacece, 

 but could not assign them any other place. Recently Dr. Wal- 

 licli has claimed that they belong to the Rhizopoda. I have not seen 

 his original paper, so that I do not know his reason for this classifica- 

 tion, but it seems to be most probably the correct one. 



I have identified the following species : Dictyocha specidum, Dicty- 

 ocha Jib ula, and a species of Mesocena, which has six external teeth 



