164 NATURAL SCIENCE. may. 



superposition of sandstones upon slates more easily affected by denu- 

 dation ; the former rock, from its containing a few obscure Brachiopod 

 fossils, discovered by Mr. White, a naturalist who spent some time in 

 the district, is considered by Dr. Derby to be of Devonian age. 

 The country between Cuyaba and the plateau is of the open kind 

 known as monte, various species of Ochna, Evythroxylon, a Cochlospevmum 

 in August leafless and one mass of golden bloom, the Vochysiaceous 

 tree Salvertia convaUarioides, Bignonias, Bromeliaceae, &c., being 

 conspicuous objects in its vegetation. A stay of two days was made 

 at the village — now much decayed — of Sta. Anna da Chapada, after 

 which the party returned by easy stages, securing specimens of the 

 rocks and Natural History objects by the way. 



A visit was subsequently paid to Santa Cruz, followed by a 

 journey in a north-west direction through the forest whence the 

 province derives its name, and where is found a great part of the 

 Ipecacuanha which reaches Europe. After considerable difficulty 

 the forest was traversed, and the party emerged upon the fine treeless 

 Campos de Tapirapuan, which are flanked by densely wooded hills 

 (Sierra de Tapirapuan) running east and west. The existence of an 

 olivine basalt in these hills was the most interesting discovery made 

 hereabouts. Returning to Santa Cruz, the party devoted ten weeks 

 to the examination of that district, and the naturalists made a large 

 collection of the rocks, plants, and animals, while Mr. John Storm 

 devoted himself to the correction of the faulty maps of this part of 

 Brazil. 



Notwithstanding the early and unexpected recall of the expe- 

 dition, we are glad to learn that some results of much scientific 

 interest may be expected from the study of the collections brought to 

 Europe. 



Ants and Mites. 



The curious habit which ants have of harbouring in their nests a 

 variety of other insects, is a well-known fact. The reason for this 

 singular exercise of hospitality is by no means always apparent ; in 

 some cases, however, it does appear to be fairly clear, particularly in 

 the case of certain mites (Gamasids), whose habits and customs are 

 treated of by Mr. A. D. Michael in the recently published part of the 

 Proceedings of the Zoological Society of London. The author of this 

 paper investigated a number of ants' nests in Corsica and in the 

 neighbourhood of Innsbruck, and in many of these nests there 

 occurred various species of Gamasids, whose relation to their host 

 formed the subject of the enquiry dealt with in the paper. The 

 nests of a small yellow ant, Tetyamoviuin avspitosum var. mevidionale, 

 were infested with two kinds of Gamasids. One species, which 

 Mr. Michael describes as new, under the name of Lcelaps equitans, was 

 not only found in the nests, but also upon the ants themselves ; and 



