204 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
The accompanying sketches (Figs. 12-10) illustrate the topography 
of the islands of Panama Bay. 
The highest of these islands are marked by three conspicuous features, 
all of which are likewise characteristic of the mainland. Тһе first of 
these is the rounded and pointed 
character of the higher summits, ex- 
actly analogous to those of the cen- 
tral portion of the Isthmus. Upon 
most of the islands where these high 
summits exist, their lower profiles ex- 
pand horizontally into distinct exten- 
FIGURE 14. Guano covered Rock, ч 3 
near South End of Taboguilla Sive benches or shoulders, standing 
Island. about 75 feet above the water at the 
sea line. These shoulders, together 
with the entire summits of some of the other islands, where the high 
pointed hills are missing, undoubtedly represent the Panama base levelled 
plain of the mainland. 
These island benches correspond to 
the Panama plain, and are terminated 
abruptly by steep vertical cliffs at the 
water’s edge, corresponding in height 
to the tidal variation of about 20 feet. 
m 4 Етогвв 15. San Jose Rock, Panama 
These cliffs are often concave in pro- So nomian o! Panata 
| у, Remnan a 
file, and it is apparent upon every side Báse Level, 
that they are produced by the intense 
wave erosion which is at present rapidly undermining them.  Fre- 
guently the beating of the waves has cut a narrow passage through 
some projecting cape, completely sev- 
ering small islets from the larger 
body with which it was but recently 
connected. Every stage in this pro- 
cess can be seen in various places. 
It seems to me that : — 
1. All of the islands of Panama 
Bay are composed in part of the an- 
cient looking, black igneous rock, 
apparently of the same character as those found upon the Isthmus, 
interassociated with the Panama formation, which can be seen upon 
the island of Naos outeropping close to the water, as at the city of 
Panama. 
Ғлагвв 16. Basaltic Rock, South 
End of Taboguilla Island. 
