276 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
PRELIMINARY DESCRIPTION OF THE SPECIMENS OF IGNEOUS Rocks IN 
THE COLLECTIONS FROM THE ISTHMUS OF PANAMA AND Costa RICA, 
MADE BY ROBERT T. HILL, JANUARY, FEBRUARY, AND Manon, 1895. 
By J. E. Wolff. 
(2) Quarry at Bujio. In the slide a much decomposed augite por- 
phyrite. Тһе slide must be from a pebble, for the hand specimen is a 
conglomerate. 
(3) Boulders of hill back of Pefia Negra, about one mile below Bujio 
on Chagres River. Both slides are of hornblende andesite, 
(5) Cut north of end of Las Cascadas siding, Panama Railroad. А 
reddish green granular rock, with green spots and chalcedone lining 
cavities. Contains fragments of feldspar and of eruptive rock.  Silicified 
tuff. 
(6) Panama Railroad, neck below “ Nigger Head " Bluff, Mata Chin. 
Basalt. 
(7) First cascade, Las Cascadas. A banded gray flinty rock. In 
the slide long laths of plagioclase feldspar crystals of magnetite, and 
abundant black irregular grains, probably the decomposed bisilicate. An 
eruptive (augite-porphyrite 7). 
(8) Panama Railroad from Nigger Head Bluff, Bas Obispo. A decom- 
posed basic eruptive hornblende-augite-andesite, or porphyrite. 
(9) 31st mile Panama Railroad. Augite-andesite. 
(10) 314 miles Panama Railroad, Bluff near Haut Obispo. (ù) Badly 
decomposed olivine basalt, or melaphyre. 
(11) 33 miles Panama Railroad. First fall of the Obispo River. A 
reddish gray trachyte with feldspar phenocrysts and green patches. 
(12) 32 miles Panama Railroad. Coarse decomposed tuff; augite 
porphyrite fragments ; calcite cement. 
(13) 31% miles, Panama Railroad cut near Bas Obispo. Tuff with 
siliceous cement and fragments of decomposed basic eruptives. 
(14) 344 miles, Panama Railroad. Empire cut. Limestone contain- 
ing shell fragments. 
(15) Panama Railroad, miles 32, cut in east and west hill. Dirty 
green decomposed augite andesite. 
(16) Panama Railroad. Drift from high mountain back of Empire 
limestone, } mile north. Dolerite (Basalt). 
(19) Panama Canal between Vamos 4 Vamos and 104 kilometers. 
A dark gray limestone containing shells. In a calcareous cement 
