CORRELATION GF FORMATIONS, 325

and Oliva litterata a maximum longitude of 82 mm. The old species present
many and numerous variations and new species seem to be in the process of
evolution,

“The facies presented in the Cape Fear region can be readily interpreted by
the hypothesis which Dr. Paul Bartsch from his extensive study of the Pyra-
midellidae? believes to hold good—that it is the ‘optimum condition that
weakens specific bonds and tends to throw an organism into the so-called
“state of flux.”’

“It seems not improbable that, with the initiation of the Pliocene and the
consequent warming of the waters, conditions for marine life became too fayor-
able for the equilibrium of a fauna adapted to the cooler waters of the Mio-
cene. Rapid development ensued, and these localities became a center of radia-
tion of later Pliocene faunas. If this hypothesis be correct, a careful study
of the fauna should reveal many precursors of later Pliocene forms. Some
have already been found, and it seems rather certain that future study will
yield results interesting both to the geologist and biologist.”

Dr. William H. Dall of the Smithsonian Institution in the Wagner
Free Institute Transactions, vol. 3, pt. 2, pp. 213-217, has given the
results of his study of the Croatan fauna. Although small collections
have subsequently been made from the Slocum’s Creek locality, no de-
terminative work has been done upon them. Dr. Dall’s list includes 96
molluscan species. Among the diagnostic post-Waccamaw species may
be noted Plicatula gibbosa Lamarck, Arca pexata Say, Arca ponderosa
Say, Arca campechiensis Dillwyn, Diplodonta subglobosa OC. B. Adams,
Ensis americana Gld., Rangia grayi Conrad, Labiosa canaliculata Say,
Barnea costata L., and Urosalpina cinereus Say. Of the significance of
their range he writes:

“In the case of the Croatan beds we find 85 uncharacteristic (Miocene to
recent) species, with 6 new or doubtful forms. We have 2 characteristic Plio-
cene species, with 11 hitherto known as recent. Of the 55 with known range,
47 are known as Pliocene or younger, and 8 as of Pliocene or older horizons.

“The Croatan beds are obviously newer than those of the Waccamaw, yet
when compared with the admitted Pleistocene beds of South Carolina, such as
those of Simmon’s Bluff, the presence on the Neuse of 41 out of 96 species
which have not been known later than the Pliocene forbids us to regard the

fauna as later than Pliocene.”

LAFAYETTE FORMATION.

The Lafayette formation of North Carolina is poorly developed and
the deposits are largely confined to a relatively narrow belt along the
eastern margin of the Piedmont Plateau, where they are found, as has
already been described, in somewhat isolated and highly dissected

 

1pyramidellide of New England and the Adjacent Region. Proc. Bos. Soc, Nat. Hist.,
vol. 34, No. 4, p. 91. ;

Pe