Crosby.] 490 [April 1 
The Caribbean group presents many points of resemblance, both 
lithological and structural, to the Taconian system of eastern North 
America, with which I have elsewhere! connected it. A correlation 
which appears to be justified, also, by its relations to the lowest Pa- 
leozoic formations. For we find that the third and highest division 
of the Caribbean group of Trinidad is overlaid on the south, with 
every appearance of unconformability, by the compact limestone which 
forms the Laventille Hills in the vicinity of Port of Spain and the 
small islands to the westward. This is entirely distinct from the 
crystalline limestone forming the middle division of the Caribbean 
group, and undoubtedly belongs to a more recent epoch than any of 
the rocks to the northward ; and hence Mr. Guppy is right in urging 
‘that it should no longer be included in the Caribbean group. The 
compact limestone is rich in organic remains; but these are so ob- 
scure that it is only within the last decade that the fact of their 
existence has been certainly recognized. We are indebted to Mr. 
Guppy almost solely for the little that is known of the paleontology 
of this rock. The fossils so far made out are small bivalves resem- 
bling Nucula, and small univalves like Murchisonia and Loxonema. 
Besides these, there are, according to Mr. Guppy, a massive reef- 
coral and many serpuline fossils. Although Mr. Guppy is inclined 
to hold a different view, I am strongly convinced that the fossils 
which I have seen from this limestone have a decidedly Cambrian — 
(Lower Silurian) aspect. Mr. Guppy has provisionally identified 
two of the Gasteropods with the North American species, Murchi- 
sonia anna Billings and Murchisonia linearis Billings, both Cambrian 
species. The limestone itself is very compact and massive, of a dark 
bluish-drab to black color, and presents a strong resemblance to the 
Trenton limestone of New York.  Interstratified with it are occa- 
sional beds, one to twenty feet thick, of soft, thin bedded slates and 
shales, which are frequently highly ferruginous and have polished 
and glistening surfaces. It is chiefly by means of these argillaceous 
beds that we are able to observe the dip of the limestone- 
Although, in the absence of fossils, and considering that an ocean 
lies between, the correlation of the Taconian system of North Amer- 
ica with the itacolumite, schist, and limestone series of Brazil on the 
one hand, and with the Caribbean group of Trinidad and the Span- 
ish Main on the other, may not be regarded as entirely satisfactory; 
1 Proc. Bost. Soc. Nat. Hist., xx., 1878, p. 55. 
