226 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
country there can be seen evidences of terraces which, if properly studied, 
could be interpreted into an interesting geologic history. The beautiful 
suburb of San José, known as the Savanna, is a small flat area composed 
of Jacustral alluvial soil, and so level that it looks as if the waters had 
only been recently withdrawn from it. In no instance is there any 
body of water now retained in the lower levels of these ancient lake 
Fiaure 28. Section of Boulder Clays, Flank of Irazu Summit, 
between San José and Cartago (Gabb). 
beds, for the modern drainage has and is now cutting deep cafions into 
them far below the last lacustral occupation. 'These streams reveal in 
their cafions and gorges the same red clays and igneous boulders so 
characteristic of the older igneous foundation encountered upon the 
Pacific coast. In addition there are mamy outcrops of massive black 
igneous rocks. The accompanying illustrations give a characteristic 
picture of the boulder topography of the lowest drainage cuts in the 
central basin (Plate XIV.). 
The San Miguel Beds. — On the south side of the east and west chain 
of bolson valleys, and standing parallel with and opposite the volcanic 
heights forming their northern border, there is another large range of 
mountains running east and west, known as the Sierra Candella. Al- 
though there is no mention of limestone formations in Costa Rica, I was 
informed that the lime used in the city was burned from the stome found 
in the base of these mountains. I visited the site of the kilns, some 
three leagues south of San José, near the villages of San Miguel and 
Desamparado. Тһе road the whole distance ascends about 400 feet 
above the city through the volcanic tuffs, including some of the later 
and whiter voleanic rocks that I had not seen elsewhere until we reach 
the foothills of the mountains. This I found to be composed almost 
entirely of a massive blue-blaek Paleozoic looking limestone which was 
being quarried at several places. The strata were much disturbed, dips 
being found in many directions, but so concealed by the vegetation that 
it was impossible to make out any systematio arrangement. The only 
conspicuous fossils that we could find after much search was a very large 
